Dirt Calculator for Soil, Topsoil and Raised Beds

Quick answer: how much dirt do I need?

For a rectangular area with length and width in feet and depth in inches:

Cubic feet = length × width × depth ÷ 12. Cubic yards = length × width × depth ÷ 324.

For example, a 4-foot by 8-foot bed with 12 inches of new fill needs 32 cubic feet, or approximately 1.185 cubic yards. That is the measured volume before any extra quantity or supplier order rounding.

Choose the calculation for your project

Choose the material as well as the measurement method. The arithmetic can be the same while the appropriate product differs. A quantity result alone does not establish whether a product suits planting, grading, or a particular construction specification.

Soil, topsoil, garden soil, and fill dirt

Soil is the broad term

Soil includes mineral and organic materials, water, air, and biological activity. USDA NRCS describes soil as a natural body that occupies space and can support rooted plants. “Dirt” is an everyday ordering term, so identify the actual product instead of assuming the name defines its properties.

Topsoil is not automatically a finished planting mix

Topsoil refers to surface soil, but products sold under that name vary. Screening removes larger pieces; it does not establish fertility, texture, or suitability on its own. University of New Hampshire Extension advises asking about origin, screening, and test data when purchasing topsoil.

Garden soil may be a blend

A packaged garden soil or bulk planting mix can contain added materials. Read its intended uses and ingredient information. A product sold for mixing into in-ground soil should not automatically be treated as a complete medium for a pot or elevated planter.

Fill dirt serves a different ordering task

For a fill project, specify the material required to occupy a missing volume. If the project includes a planting layer, calculate that layer separately. For specified structural fill or backfill, the project's material and compaction requirements determine suitability; this volume estimate does not select those requirements.

Measure the space that will actually receive soil

Use inside dimensions for raised beds

Measure between the inside faces of the walls. Outside dimensions include wall thickness, which can overstate the soil capacity. Also account for internal dividers or other parts that occupy measurable space.

Use fill depth rather than wall height

Decide where the soil surface should finish. If the wall is 18 inches high but the intended fill is 16 inches, calculate 16 inches. If suitable soil already occupies the bottom, measure the remaining depth to the intended surface.

Keep the units visible

Feet and inches can be used together only after the depth conversion is included. A 12-inch depth equals 1 foot. Entering 12 as feet instead of inches makes the estimate twelve times too large.

How to calculate soil volume

From length, width, and depth

Multiply the length by the width to find area. Convert depth to feet, then multiply by that area. Divide cubic feet by 27 to obtain cubic yards.

A 6-foot by 10-foot planting area with an assumed 4-inch layer needs:

6 × 10 × 4 ÷ 12 = 20 ft³ = approximately 0.741 yd³.

From an area you already know

If you already have the area in square feet, do not multiply by length and width again. Use:

Cubic feet = area in square feet × depth in inches ÷ 12.

Cubic yards = area in square feet × depth in inches ÷ 324.

For a round bed

Find the area from the inside diameter, then apply depth. With diameter in feet and depth in inches:

Cubic feet = π × (diameter ÷ 2)² × depth ÷ 12.

A 6-foot-diameter bed filled to an assumed 8-inch depth needs approximately 18.850 ft³, or 0.698 yd³. Keep the full calculation precision until the final display.

Garden bed dirt calculator: new beds and top-ups

After calculating the soil layer, estimate the separate surface cover with the mulch calculator. Enter the existing mulch depth so the top-up does not charge for a complete new layer.

A new bed may need its whole intended planting volume. An established bed usually needs only the missing layer or the amendment quantity you intend to add. Measuring the deficit avoids ordering enough material to fill an already occupied bed again.

For an 8-foot by 4-foot bed that is uniformly 2 inches below its intended soil level:

8 × 4 × 2 ÷ 12 = approximately 5.333 ft³.

If the level varies, take several depth measurements and divide the bed into sections where needed. A single deep spot should not be used as the depth for the entire bed.

Topsoil calculator: estimate the layer you will add

Calculate the actual area receiving topsoil. Exclude a patio, path, existing bed, or other area that will not receive that layer. Use the planned added depth, not the depth of all soil beneath it.

For an assumed 750-square-foot area with a 3-inch topsoil layer:

750 × 3 ÷ 12 = 187.5 ft³ = approximately 6.944 yd³.

The 3-inch depth is an example. Choose an appropriate layer for the purpose, existing soil, and product instructions rather than adopting one depth for every lawn or garden.

How much area does one yard of topsoil cover?

One cubic yard equals 27 cubic feet. Coverage changes with layer thickness:

Area in square feet = cubic yards × 324 ÷ depth in inches.

These are calculated layer volumes before settlement, uneven-ground adjustments, or losses. The table does not recommend these depths for a specific crop, lawn, or installation.

Raised bed soil calculator: one bed or several

Calculate each bed's inside dimensions and intended new fill depth. For identical beds, multiply one bed's volume by the number of beds. For different sizes, calculate each separately before adding the results.

These depths and bag sizes are examples. A bag count rounds upward to whole bags; the geometric volume does not. For two identical 4-by-8-foot beds filled to 6 inches, the total is 32 ft³, rather than 16 ft³.

Choose a raised-bed mix for the actual setting

A bed open to suitable native soil and a planter isolated on a hard surface are different growing environments. University of Maryland Extension gives separate approaches based on existing soil and whether the bed sits on a nonpermeable surface. Use guidance that matches your setting.

University of Minnesota Extension describes topsoil-and-plant-based-compost proportions ranging from roughly two-thirds topsoil with one-third compost to equal portions. That is guidance to consider, not proof that one blend suits every site. Soil texture, ingredients, and the plants you will grow still matter.

Oregon State University Extension advises using a soil mixture rather than filling a framed bed with compost alone. It also explains that compost decomposition can lower the level over time. An adjustable mix calculation should therefore measure ingredients without promising a permanent finished level.

Worked example: two different beds and a soil-compost mix

Calculate the combined volume

Assume Bed A measures 4 by 8 feet inside and needs 12 inches of new fill. Bed B measures 3 by 6 feet and needs 8 inches. Their volumes are 32 ft³ and 12 ft³, respectively.

Combined volume = 32 + 12 = 44 ft³, or approximately 1.630 yd³.

Divide the total into a selected blend

For this example, choose a 2:1 topsoil-to-compost ratio by loose ingredient volume. Divide the total into three equal parts. Topsoil receives two parts and compost receives one.

This is an illustrative allocation, not a site-specific growing recommendation. Loose ingredient volumes are an ordering approximation; blending and settlement can change the final occupied volume.

Keep purchased surplus separate from the mix

The rounded bags provide 30 ft³ of topsoil and 15 ft³ of compost, or 45 ft³ total. Keep the planned ingredient quantities and the package surplus visible. A different bag combination may create unequal surpluses, so pouring in every bag can change the intended ratio.

How many bags of soil do I need?

Find the volume needed and divide by the actual volume per bag. Then round upward:

Whole bags = round up(required volume ÷ volume per bag).

For a 32-ft³ bed and an assumed 1.5-ft³ bag, 32 ÷ 1.5 is approximately 21.333 bags. You would buy 22 whole bags, providing 33 ft³ of labeled volume. The extra 1 ft³ comes from package rounding, not a separate settlement allowance.

Topsoil bags: calculate by labeled volume

A bag of soil may show both weight and volume, but volume is the useful starting point for filling a measured space. Do not assume that every 40-pound bag supplies the same cubic-foot yield. Moisture and the product itself affect the relationship between weight and volume.

Scotts' manufacturer page lists a 0.75-ft³ size for its Premium Topsoil and identifies it as an in-ground soil conditioner. It also states that the product is not for container gardening. This is a verified example of one product's volume and use restrictions, not a recommendation for every bed.

For a geometric requirement of 9 ft³, packages labeled 0.75 ft³ would give 9 ÷ 0.75 = 12 bags, before additional allowances. Follow the specific product's directions if it gives application coverage rather than treating every product as plain bulk soil.

How many bags are in a cubic yard?

One cubic yard equals 27 cubic feet. The same yard requires different bag counts depending on package volume.

The bag sizes in this comparison are mathematical inputs, not a verified inventory at a particular store. Fourteen 2-ft³ bags provide more than one yard because 13.5 bags cannot be purchased as whole packages.

Bags labeled in liters or quarts

For a liter-labeled product, convert the required volume to liters before dividing by the package size. One cubic foot equals 28.316846592 liters, derived from the international foot definition. A 32-ft³ requirement is approximately 906.139 liters, so hypothetical 40-liter bags would require 23 whole bags.

If the package uses quarts, identify the actual unit or use another volume printed on the label. US dry quarts and US liquid quarts are different units. NIST lists both, so a soil bag should not automatically be converted using a kitchen liquid-quart factor.

Buying garden soil in a large quantity

For a large order, request a quote for the product and volume you calculated. Confirm whether the supplier sells a finished blend or separate ingredients. A price for unamended topsoil cannot be compared directly with a quote for a different planting mix.

Ask how the supplier measures the sale quantity and what order increments apply. Include delivery, minimum quantity, and unloading arrangements in the comparison. The cheapest unit price can produce a higher total if the minimum order greatly exceeds your requirement.

Compare bagged soil with bulk delivery

Bagged material

Multiply the whole-bag count by the price per bag. Use the package size of the quoted product. Add any applicable delivery or other charges separately.

Bulk material

Multiply the actual order quantity in cubic yards by the price per yard. Add delivery and other quoted charges. Keep the calculated need separate from a supplier's minimum order or rounding increment.

Example comparison using hypothetical quotes

Assume you need 44 ft³ of the same suitable finished mix. At a hypothetical 2-ft³ bag size and $6 per bag, 22 bags cost $132. A hypothetical 1.75-yd³ bulk order at $45/yd³ plus $60 delivery costs $138.75 and supplies 47.25 ft³.

These are invented prices for demonstrating arithmetic, not current US price benchmarks. In this example, bags cost less despite the bulk material's lower cost per cubic foot. Compare actual quotes for equivalent material and all included charges.

Fill dirt calculator: calculate the missing volume

Measure the area and depth of the space to be filled. If the finished area also needs a topsoil layer, remove that layer's planned volume from the fill requirement and calculate it separately. Counting the full hole as fill and then adding a planting layer on top can overstate the intended finished height.

For an assumed rectangular fill area 24 feet long, 18 feet wide, and 10 inches deep:

24 × 18 × 10 ÷ 12 = 360 ft³, or approximately 13.333 yd³.

This is the geometric void volume. Delivered loose volume and finished compacted volume may differ, so use the applicable project or supplier factor only when its basis is known.

Estimate uneven fill without using one deep measurement

A uniformly sloping rectangular gap can be estimated from its average depth. If it changes evenly from 4 inches to 8 inches, its average depth is 6 inches. This works because the depth change is linear over the area.

An assumed 20-foot by 15-foot area at that average depth needs:

20 × 15 × 6 ÷ 12 = 150 ft³, or approximately 5.556 yd³.

For irregular depressions, divide the footprint into smaller sections and estimate each separately. A simple average of a few arbitrary depths may miss where most of the area lies. More complex grading requires a better surface measurement than a single rectangular estimate. For other measured shapes and standalone volume conversions, use the cubic yard calculator.

Extra order quantity and settlement are different calculations

Adding an extra order allowance

An extra quantity percentage increases the calculated requirement:

Order volume = calculated volume × (1 + extra percentage ÷ 100).

With a hypothetical 10% extra allowance on the 360-ft³ fill example, the order estimate becomes 396 ft³, or approximately 14.667 yd³. The added 36 ft³ is a planning allowance; it does not establish a measured settlement rate.

Allowing for a known reduction in loose volume

If an applicable assumption says the delivered loose volume will decrease by 20%, only 80% remains as finished volume. The inverse calculation is:

Loose volume needed = finished volume needed ÷ (1 − reduction percentage ÷ 100).

For a target of 12 yd³ and a hypothetical 20% volume reduction, the loose requirement is 15 yd³. Adding 20% instead would give 14.4 yd³, which is a different calculation. Neither percentage is a recommended universal soil factor.

Avoid applying the same adjustment twice

Identify what the supplier's density, volume factor, or order advice already includes. Do not combine overlapping settlement factors and extra quantity percentages without understanding their purposes. Keep the base need, adjustment, and order rounding visible as separate amounts.

For delivery-unit and access questions, use the bulk delivery ordering guide.

Convert soil volume to weight only with density

Cubic yards measure volume, while tons measure mass. The conversion requires the bulk density for the specific product and condition. A universal soil weight would misrepresent differences between products and moisture conditions.

US short tons = cubic yards × bulk density in US short tons per cubic yard.

At an explicitly hypothetical density of 1.2 US short tons/yd³, 2.5 yd³ corresponds to 3 US short tons. Use the site's Cubic Yards to Tons Converter for detailed unit conversions and reverse calculations; verify the supplier's density first. If the supplier already quotes a known volume or mass, use the cubic yards to tons converter with the applicable soil density.

Check soil quality before placing a large order

Quantity and quality answer different questions. University of New Hampshire Extension recommends asking for the source of purchased topsoil and test information, including pH and texture. If it is amended, ask what was blended into it.

For a planting project, soil-test results can guide amendments. University of Maryland Extension recommends testing existing soil when planning raised beds. A volume calculator cannot determine fertility or the right fertilizer rate from bed dimensions alone.

Keep an order worksheet

Record each area before combining quantities. This makes it easier to update the order when a bed size, fill depth, product, or package volume changes.

Also record the density if ordering by weight, the ingredient proportions if mixing, and the quote date if comparing cost. Keep the full calculation precision until the final order increment is applied.

Common soil-ordering mistakes

Measuring the outside of the bed

Wall thickness is not soil space. Use inside measurements and the actual depth to the desired fill line. For a top-up, calculate only the additional material.

Applying one bag size to every product

A bag's cubic-foot or liter volume determines its geometric yield. Enter the package you intend to buy rather than a fixed bag assumption. Whole-bag rounding can add surplus even when no extra allowance is selected.

Using a planting mix as unspecified fill

Choose material according to the project. Keep planting and fill quantities separate when both are needed. A soil calculator estimates volume; it does not establish that two products are interchangeable.

Treating blend percentages as weight percentages

The ingredient examples here use volume. A two-thirds volume share does not imply a two-thirds weight share because components can have different bulk densities. Label the ratio basis when asking a supplier to prepare a mix.

Calculation and scope notes

Sources. Geometry, coverage tables, bag counts, and worked examples are original calculations. Example depths, prices, densities, bag sizes except the identified manufacturer example, and adjustment percentages are assumptions. They are not live supplier quotes or universal installation instructions.

Frequently asked questions

How much soil does a 4-by-8 raised bed need?

At 12 inches of new fill, it needs 32 ft³, or approximately 1.185 yd³. At 6 inches, it needs 16 ft³. Measure the bed's inside dimensions and the depth you actually intend to add.

Is a topsoil calculator different from a dirt calculator?

The underlying volume formula is the same. What differs is the material and project: a topsoil layer, a new planting bed, or a fill area. Use the appropriate depth, product, and ordering assumptions.

How many bags of soil do I need for two beds?

Add the required volumes first, then divide by the actual bag size if both beds use the same product. If ingredients or products differ, calculate their bag counts separately. Round to whole bags only after each product's total is known.

Do I need to buy soil for the full height of an existing bed?

Only if you are replacing the entire intended soil volume. Otherwise, measure the missing depth or the layer you plan to add. Existing suitable soil reduces the new quantity needed.

Can I calculate the compost separately?

Yes. For a chosen blend, multiply the total planned loose ingredient volume by the compost's volume share. For a separate amendment layer, calculate area times the layer depth instead; do not count it both ways.

How many cubic feet are in a yard of dirt?

A cubic yard equals 27 cubic feet. “Yard” in a bulk soil order usually refers to a cubic yard, but confirm the supplier's unit. Weight still depends on the material's bulk density.

Should I always order extra for settling?

There is no universal percentage for every product and condition. Ask what allowance or volume conversion is appropriate for your project. Keep an extra order allowance distinct from a specified reduction in loose volume.

Can a garden soil product go into an elevated planter?

Check the product's labeled intended use and guidance for that growing environment. A mix intended to amend native soil may not be suitable as the entire medium in an isolated planter. The same volume calculation can apply without making the materials equivalent.