Calculate Your Topsoil Order Without Guessing

Work your own numbers. The Mortar Desk material coverage calculator converts area and depth to cubic yards, tons and bag count for ten materials, with the density it uses cited on every row.

The short answer: calculate area, depth, and order volume

To estimate how much topsoil you need, start with two inputs:

1. The area to cover
2. The intended topsoil depth

For an area measured in square feet and a depth measured in inches, use:

Cubic yards = square feet × depth in inches ÷ 324

If you do not know the square footage of a rectangular area, calculate it first:

Square feet = length in feet × width in feet

These formulas follow the standard workflow of converting the depth to feet, calculating cubic feet, and dividing by 27 to obtain cubic yards, as shown in the Inch Calculator soil-volume guide.

For example, a 20 × 30-foot lawn has an area of 600 square feet. At a depth of 2 inches:

600 × 2 ÷ 324 = 3.70 cubic yards

That is the unadjusted geometric volume. If the supplier sells only whole cubic yards, the practical purchase quantity would be 4 cubic yards before any separate allowance.

Choose the project type before choosing the depth. A light lawn topdressing may need only a fraction of an inch, while preparing a new lawn, refreshing a planting bed, or filling an empty raised bed can require substantially more. Because volume changes in direct proportion to depth, an unsuitable depth assumption can affect the order more than a small measuring error.

Use the output unit that matches how the soil is sold:

• Cubic feet are useful for bagged products.
• Cubic yards are commonly used for bulk orders in the United States.
• Cubic metres may be used for bulk orders in metric markets.

Manual topsoil calculator worksheet

A calculator-style estimate can be completed with the following inputs.

Enter either:

• Total area in square feet; or
• Length in feet × width in feet.

Then enter:

• Intended depth in inches;
• Optional allowance: 0%, 5%, or 10%;
• Supplier increment, such as whole yards, half-yards, quarter-yards, or whole bags; and
• Labeled bag volume if buying bags.

Calculate:

1. Base cubic feet Area in square feet × depth in inches ÷ 12

2. Base cubic yards Base cubic feet ÷ 27

3. Adjusted planning volume Base volume × 1.00, 1.05, or 1.10

4. Purchase quantity Adjusted volume rounded up to the available bulk increment or next whole bag

Keep those outputs separate. If the base calculation produces 7.41 cubic yards, a 10% scenario produces 8.15 cubic yards, and the supplier sells only whole yards, the figures are:

• Base geometric volume: 7.41 cubic yards
• Adjusted planning volume: 8.15 cubic yards
• Purchase quantity: 9 cubic yards

The final figure is not a more accurate measurement of the site. It includes both a selected planning allowance and supplier rounding.

Every result remains an estimate. Dimensions may be approximate, ground levels may vary, placed soil may settle, and suppliers may sell only in set increments. The calculation establishes a defensible starting volume; it does not guarantee the exact quantity needed to produce a particular finished grade.

Choose the topsoil depth before calculating

If the area remains unchanged, doubling the depth doubles the required volume. A 600-square-foot area requires approximately 3.70 cubic yards at 2 inches but approximately 7.41 cubic yards at 4 inches.

The appropriate starting depth depends on what the soil is intended to do. It can also be affected by the existing soil, plant requirements, intended finished grade, and whether material is being added, replaced, or used to fill an empty structure.

Project	Starting depth to investigate	Important distinction
Light lawn topdressing	About 1/4–1/2 inch	A thin surface application, not a new lawn base
Broader lawn refresh or repair	About 1–2 inches	May involve reseeding, renovation, or distributed low areas
New lawn or sod preparation	Commonly 4–6 inches	A planning range rather than a universal specification
Refreshing an existing bed	Roughly 3–6 inches	Existing soil remains beneath the added material
New planting layer over existing soil	Around 6 inches as a starting point	Plant requirements and existing soil may justify another depth
Raised bed	Measure the intended growing-medium or fill depth	Do not assume the complete volume should be straight topsoil
Low areas	Measure the missing depth	Different zones may require different quantities

Light topdressing and new-lawn preparation are different operations. Commercial landscaping guidance commonly describes light lawn topdressing as approximately 1/4–1/2 inch and new-lawn preparation as roughly 3–6 inches; these are planning ranges, not site specifications (Mulch and More).

Broader lawn-refresh guidance may extend to 1–2 inches, while low-area depth depends on the amount of grade that is actually missing. One supplier guide, for example, distinguishes 1–2-inch lawn refreshing from deeper new-lawn preparation and recommends measuring irregular spaces separately (St. Louis Topsoil).

For an existing garden, roughly 3–6 inches may be used as an initial range when refreshing the surface. That recommendation applies to adding material to a garden that already has soil beneath it, not to filling an empty structure (Inch Calculator).

A new planting layer over existing soil may begin around 6 inches in some gardening guidance. Raised-bed recommendations may instead refer to a 6–12-inch growing layer, with the required depth varying by what is being grown and what already exists below (Almanac topsoil guide).

These figures should not be combined into one universal recommendation.

Light lawn topdressing is not the same as lawn establishment. A shallow layer is intended as a surface application. Guidance extending to 1–2 inches generally describes broader refreshing, repair, low-area filling, or renovation. Before placing a deeper layer over living grass, clarify whether the project is truly topdressing or whether the lawn is being rebuilt.

For a new lawn or sod preparation, 4–6 inches is a commonly cited planning range. It is not automatically correct for every yard. Existing grade, soil condition, planned excavation, drainage, and installation method all matter. Selecting the deepest number in a general table does not correct an underlying grading or soil problem.

For an existing garden bed, adding roughly 3–6 inches of material is different from creating an entirely new growing profile. A deeper new bed depends on the intended plants, available root space, existing soil, and whether the work involves amendment, replacement, or complete filling.

Raised-bed recommendations appear inconsistent because they often answer different questions:

• Some describe adding a 6–12-inch growing layer over existing material.
• Some describe filling an empty bed to its full internal depth.
• Others recommend a deeper total growing profile for particular plants.

For an empty raised bed, measure the actual internal depth from the base or lower fill layer to the intended finished soil level. Do not select a generic raised-bed depth simply because it appears in a table.

The geometric calculation gives the total volume of the space being filled. It does not establish that every cubic foot should be straight topsoil. Confirm the intended growing-medium composition before dividing the total among topsoil, compost, or other specified components.

For low spots, measure the depth actually missing. If one section is 1 inch low and another is 4 inches low, applying a 4-inch depth to the entire area will overstate the volume. Divide the ground into zones or use an average supported by several measurements.

Whatever range you begin with, define what the selected depth means:

• Loose soil immediately after placement;
• Desired depth after settling;
• Depth of topsoil alone; or
• Complete depth of a blended growing medium.

Write down that definition before calculating. Otherwise, two quotes based on the same nominal depth may represent different quantities.

Topsoil formulas in cubic feet, cubic yards, and cubic metres

The full workflow makes the unit conversions visible and helps catch mistakes.

Imperial calculation

First calculate area:

Area in square feet = length in feet × width in feet

Convert depth from inches to feet:

Depth in feet = depth in inches ÷ 12

Calculate cubic feet:

Cubic feet = area in square feet × depth in feet

Convert cubic feet to cubic yards:

Cubic yards = cubic feet ÷ 27

One cubic yard is a 3 × 3 × 3-foot volume, so it contains 27 cubic feet. The same conversion and dimensional method are shown in the Alluvial Soil Lab soil-calculation guide.

For a 10 × 4-foot bed at 6 inches:

1. Area: 10 × 4 = 40 square feet
2. Depth: 6 ÷ 12 = 0.5 foot
3. Volume: 40 × 0.5 = 20 cubic feet
4. Cubic yards: 20 ÷ 27 = 0.7407 cubic yard

Deriving the shortcut

When the area is already in square feet and the depth is in inches:

Cubic yards = square feet × inches ÷ 12 ÷ 27

Because 12 × 27 = 324:

Cubic yards = square feet × depth in inches ÷ 324

The units matter. Multiplying a length and width measured in feet directly by a depth measured in inches does not produce cubic feet. If the depth is not divided by 12, the result is twelve times too large.

For example:

• Incorrect: 600 square feet × 4 inches = 2,400 “cubic feet”
• Correct: 600 × (4 ÷ 12) = 200 cubic feet

Then:

200 ÷ 27 = 7.4074 cubic yards

Metric calculation

In metric units, convert every dimension to metres:

Cubic metres = length in metres × width in metres × depth in metres

If depth is measured in millimetres, divide it by 1,000:

150 mm ÷ 1,000 = 0.15 m

For an area measuring 10 × 15 metres at 150 mm:

10 × 15 × 0.15 = 22.5 cubic metres

This matches the worked method in Rolawn’s topsoil requirement guide.

Retain the original measurements and unrounded conversions through the calculation. Round only the final volume. Replacing the exact conversion 4 ÷ 12 with 0.33 too early, for example, slightly understates the result.

Topsoil coverage and bag conversions

One cubic yard contains 27 cubic feet. Spread over a flat area, its coverage decreases in direct proportion to depth.

Topsoil depth	Approximate coverage from 1 cubic yard
1 inch	324 square feet
2 inches	162 square feet
3 inches	108 square feet
4 inches	81 square feet

These values are direct results of the cubic-yard formula. At 1 inch, 27 cubic feet spread over 324 square feet creates a layer 1/12 foot deep. Doubling the depth halves the area covered.

You can reverse the table to estimate cubic yards:

Required cubic yards = total square feet ÷ coverage per cubic yard at the selected depth

The direct formula is preferable for custom depths, but the table provides a useful check.

Converting volume into bags

Use the volume printed on the package:

Number of bags = required cubic feet ÷ labeled cubic feet per bag

Apply any selected allowance to the required cubic feet first. Then divide by the bag volume and round up to the next whole bag.

Suppose a project requires 25 cubic feet and the selected product contains 0.75 cubic foot per bag:

25 ÷ 0.75 = 33.33 bags

The purchase quantity is therefore:

34 bags before any separate allowance

Do not assume every bag contains 0.75 cubic foot—or any other standard amount. Garden-center listings include products in several package volumes, so the calculation must use the selected product’s label (Mahoney’s soil and mulch calculator).

Bag weight is not a dependable substitute for labeled volume. Soil density changes with moisture, composition, and compaction, so two products of equal weight need not contain equal volumes.

Mathematically, one cubic yard is equivalent to:

• 27 bags containing 1 cubic foot each;
• 18 bags containing 1.5 cubic feet each; or
• 13.5 bags containing 2 cubic feet each.

The last result requires 14 whole bags to equal or exceed one cubic yard. These are mathematical equivalents, not assumptions about the sizes stocked by a particular store.

Checked examples for lawns, beds, and raised beds

The examples below keep the measured volume, optional allowance, and supplier-rounded purchase quantity separate. Purchase quantities are illustrations; use the increments offered by the supplier.

Example 1: Lawn repair, 20 × 30 feet at 2 inches

• Inputs: 20 ft × 30 ft × 2 in
• Unit conversion: Area = 600 ft²; depth = 2 ÷ 12 = 0.1667 ft
• Base geometric volume: 600 × 2 ÷ 324 = 3.70 yd³, equivalent to 100 ft³
• Optional allowance: 0% = 3.70 yd³
• Supplier-rounded purchase amount: 4 yd³ if sold only in whole cubic yards

This assumes a uniform 2-inch layer. If the project consists of variable low spots, calculate those zones separately.

Example 2: Deeper lawn or planting layer, 20 × 30 feet at 4 inches

• Inputs: 20 ft × 30 ft × 4 in
• Unit conversion: Area = 600 ft²; depth = 4 ÷ 12 = exactly 1/3 ft
• Base geometric volume: 600 × 4 ÷ 324 = 7.41 yd³, equivalent to 200 ft³
• Optional allowance: 5% = 7.78 yd³; 10% = 8.15 yd³
• Supplier-rounded purchase amount: At whole-yard increments, 8 yd³ for the 5% scenario or 9 yd³ for the 10% scenario

Keep 4/12 as an exact fraction through the calculation. Replacing it prematurely with 0.33 gives 198 cubic feet and 7.33 cubic yards, understating the geometric volume.

Example 3: Garden bed, 10 × 4 feet at 6 inches

• Inputs: 10 ft × 4 ft × 6 in
• Unit conversion: Area = 40 ft²; depth = 6 ÷ 12 = 0.5 ft
• Base geometric volume: 40 × 0.5 = 20 ft³, or 20 ÷ 27 = 0.74 yd³
• Optional allowance: 0% = 20 ft³, or 0.74 yd³
• Supplier-rounded purchase amount: 1 yd³ if bulk soil is sold only by the whole yard; for bags, divide 20 ft³ by the labeled bag volume and round up

Example 4: Raised bed, 4 × 8 feet filled to 12 inches

• Inputs: 4 ft × 8 ft × 12 in
• Unit conversion: Area = 32 ft²; depth = 12 ÷ 12 = 1 ft
• Base geometric volume: 32 × 1 = 32 ft³, or 32 ÷ 27 = 1.19 yd³
• Optional allowance: 0% = 1.19 yd³
• Supplier-rounded purchase amount: 1.25 yd³ if quarter-yard increments are available, or 2 yd³ if only whole yards are sold

The calculated 32 cubic feet represents the entire measured fill space. It does not mean the bed must contain 32 cubic feet of straight topsoil.

Example 5: Larger area, 1,000 square feet at 4 inches

• Inputs: 1,000 ft² × 4 in
• Unit conversion: Depth = 4 ÷ 12 = 1/3 ft
• Base geometric volume: 1,000 × 4 ÷ 324 = 12.35 yd³, equivalent to 333.33 ft³
• Optional allowance: 0% = 12.35 yd³
• Supplier-rounded purchase amount: 13 yd³ if sold in whole-yard increments

With a 5% scenario, the adjusted quantity is approximately 12.96 cubic yards, which still rounds to 13 whole yards. With a 10% scenario, it is approximately 13.58 cubic yards and rounds to 14 whole yards.

Example 6: Metric project, 10 × 15 metres at 150 mm

• Inputs: 10 m × 15 m × 150 mm
• Unit conversion: 150 mm ÷ 1,000 = 0.15 m
• Base geometric volume: 10 × 15 × 0.15 = 22.5 m³
• Optional allowance: 0% = 22.5 m³
• Supplier-rounded purchase amount: 23 m³ if sold only in whole cubic metres

If half-cubic-metre increments are available, the purchase quantity could remain 22.5 cubic metres. Confirm the actual increment instead of assuming whole units.

Measure irregular areas and multiple sections

For an L-shaped yard, several beds, or a project with varying depths, divide the space into simple measurable sections. Do not measure one large bounding rectangle if it includes ground that will not receive soil.

For an L-shaped lawn:

1. Split the shape into two non-overlapping rectangles.
2. Measure the length and width of each rectangle.
3. Assign the applicable depth to each section.
4. Calculate each section’s volume.
5. Add the results.

A worksheet keeps the process auditable:

Section	Length	Width	Depth	Cubic feet	Cubic yards
Lawn A
Lawn B
Bed 1
Bed 2
Total

Calculate volume separately whenever depths differ. Adding all square footage first and applying one depth is valid only if every section receives that depth.

For low or uneven ground, divide the area into shallow, medium, and deep zones. Take several depth measurements in each zone instead of relying on the deepest point. An average can be useful where variation is gradual, but it should be supported by multiple measurements.

Do not use one generic average when a small, deep hole is materially different from a broad, shallow depression. A 10-square-foot hole that is 8 inches deep should not cause an entire 500-square-foot area to be calculated at an 8-inch depth.

A calculator that supports multiple areas can total the sections, but verify that:

• Every length and width uses the selected unit;
• Every depth is entered in the correct unit;
• Sections do not overlap;
• No covered area has been omitted; and
• Each section uses its own intended depth.

This method is suitable for measurable sections and moderate variation. It should not be treated as a precise grading calculation for complex slopes, drainage work, or substantial elevation changes without site-specific information.

Allow for settling, uneven ground, and order increments

The formula result is the base geometric volume. It is not automatically the quantity you should purchase.

Some projects justify rounding up because of:

• Measurement uncertainty;
• Small variations in grade;
• Soil settling after placement; or
• The supplier’s minimum and available order increments.

A 5–10% allowance can be compared as an optional planning scenario, but it is not a mandatory waste factor.

Use:

5% adjusted volume = base volume × 1.05

or:

10% adjusted volume = base volume × 1.10

Apply adjustments in this order:

1. Calculate the base geometric volume.
2. Apply the selected allowance, if any.
3. Round to the supplier’s available increment or the next whole bag.

For a base volume of 7.41 cubic yards:

• Base volume: 7.41 yd³
• 5% scenario: 7.78 yd³
• 10% scenario: 8.15 yd³
• Whole-yard purchase quantity: 8 yd³ or 9 yd³, respectively

Do not describe the difference between 7.41 and 9 cubic yards simply as “soil required.” Part of that difference is a planning allowance, and part is supplier rounding.

A zero allowance may be reasonable when measurements and finished levels are tightly controlled and the supplier offers a suitable increment. Conversely, visibly uneven ground may justify more direct measurements rather than an arbitrary percentage.

Avoid assuming that every soil settles by one fixed rate. Loose volume and finished settled depth are not interchangeable, and soil behavior varies with moisture, composition, placement, and compaction.

Before ordering, confirm:

• Whether the selected depth means loose placed depth or desired finished depth;
• Whether the material will be compacted or merely spread;
• The supplier’s minimum quantity;
• Whether partial cubic yards or cubic metres are available; and
• Whether bag counts or bulk increments will force additional rounding.

Convert the estimate into a practical order

Bagged soil can be convenient for a small repair, a separately accessible bed, or work completed in stages. Bulk soil may be more practical once the estimate reaches several cubic yards, but there is no universal quantity at which bulk becomes cheaper.

Compare the complete local price using:

• Price per cubic foot, cubic yard, or cubic metre;
• Delivery charge;
• Minimum bulk quantity;
• Bag or bulk order increments; and
• The unused material created by rounding.

For bags, use the labeled package volume. Do not infer volume from bag weight or assume every product uses the same bag size.

For bulk orders, verify the quoted unit. A supplier may quote in:

• Cubic yards;
• Cubic metres;
• Tons; or
• Tonnes.

A price per ton cannot be compared directly with a price per cubic yard without a product-specific conversion. Volume is the more dependable basis for this calculation because the measured space is a volume, while soil weight changes with moisture, composition, density, and compaction.

If a supplier sells by weight, ask for that product’s bulk density or stated volume per ton or tonne. Use the supplier’s specification and label the conversion approximate. Bulk density varies by soil type, composition, and moisture, so product specifications should be checked before converting volume to weight (Rolawn).

Ask the supplier to confirm:

• Product name and description;
• Blend composition;
• Labeled bag volume;
• Product-specific bulk density if sold by weight;
• Minimum order;
• Delivery charge;
• Available quantity increments; and
• Whether quoted volume is measured loose.

Pre-order worksheet

Complete this before requesting prices:

• Measured sections: Length, width, and area for every zone
• Selected depth: Including whether it means loose depth, finished depth, topsoil depth, or total growing-medium depth
• Base volume: Cubic feet, cubic yards, or cubic metres
• Optional allowance: 0%, 5%, or 10%, with the selected scenario recorded
• Adjusted volume: Base volume multiplied by the selected allowance
• Rounded purchase quantity: Whole bags or an available bulk increment
• Unit of sale: Cubic feet, cubic yards, cubic metres, tons, or tonnes
• Supplier specifications: Bag volume, blend composition, bulk density where needed, minimum order, and delivery terms

Mortar Desk provides general reference calculations. It is not a contractor and does not provide engineering advice, as stated on the About Mortar Desk page. Complex grading, persistent drainage problems, or substantial changes in elevation may require site-specific professional assessment.

Frequently asked questions

How many cubic yards of topsoil do I need for 1,000 square feet?

It depends on depth:

Cubic yards = 1,000 × depth in inches ÷ 324

Depth	Base geometric volume
1 inch	3.09 yd³
2 inches	6.17 yd³
3 inches	9.26 yd³
4 inches	12.35 yd³
6 inches	18.52 yd³

The 2-, 4-, and 6-inch results align with published 1,000-square-foot examples of approximately 6.2, 12.3, and 18.5 cubic yards, respectively (Cowboy Topsoil).

These figures exclude any allowance and supplier rounding. At 4 inches, the base volume is approximately 12.35 cubic yards; a whole-yard purchase would be 13 cubic yards with no separate allowance.

How much area does one cubic yard of topsoil cover?

One cubic yard covers approximately:

• 324 square feet at 1 inch
• 162 square feet at 2 inches
• 108 square feet at 3 inches
• 81 square feet at 4 inches

These coverage figures follow from the 27-cubic-foot volume of one cubic yard and are also summarized in this topsoil coverage guide.

Coverage is inversely proportional to depth. Doubling the depth halves the area covered.

How many bags of topsoil equal one cubic yard?

One cubic yard equals 27 cubic feet, so the answer depends on the labeled bag volume:

• 27 one-cubic-foot bags;
• 18 1.5-cubic-foot bags; or
• 13.5 two-cubic-foot bags mathematically, meaning 14 whole bags to equal or exceed one cubic yard.

These equivalents and the need to calculate from the selected bag volume are summarized in the bag and bulk topsoil guidance.

Use:

27 cubic feet ÷ labeled cubic feet per bag

Do not calculate bag volume from weight unless the manufacturer or supplier provides a product-specific density conversion.

Should I add 5% or 10% to my calculated topsoil quantity?

Treat 0%, 5%, and 10% as comparison scenarios, not as fixed rules.

Calculate all three if the appropriate allowance is uncertain:

• 0%: Base geometric volume only
• 5%: Base volume × 1.05
• 10%: Base volume × 1.10

Then compare the results with the supplier’s selling increments. A whole-yard minimum may already create some additional volume without a separate allowance.

Do not use 10% as a substitute for measuring clearly different shallow and deep areas. Calculate those areas separately first.

How much topsoil can I put over an existing lawn?

For light lawn topdressing, approximately 1/4–1/2 inch is a commonly cited starting range. Guidance extending to 1–2 inches generally concerns broader refreshing, repair, low-area filling, reseeding, or renovation rather than routine light topdressing (Mulch and More).

Do not confuse these shallow applications with the commonly cited 4–6-inch planning depth for establishing a new lawn or preparing for sod. If the intended layer would bury existing grass, clarify whether the turf is being topdressed, repaired in stages, removed, or replaced.

The reliable ordering process is always the same: choose a defensible project depth, calculate the unadjusted volume with consistent units, and convert that result into the supplier’s actual selling unit. Preserve the base estimate, optional allowance, and rounded purchase quantity as separate figures so a planning buffer—or an approximate conversion from volume to weight—is never mistaken for measured volume.