Topsoil Calculator

1. Pick Imperial or Metric, the shape and the project. Enter the length and width (or diameter) and the depth of new soil you want after firming.
2. Add a settling allowance if you want extra, and set the topsoil share if you are blending in compost.
3. Choose bulk or bags, give the bag size by volume or weight, enter your own price, and read the volume, bag count, weight and cost.

A topsoil calculator is a volume tool for growing soil. It turns the size of a lawn, raised bed or garden and the depth of soil you need into cubic yards or bags to buy.

Topsoil is the upper, darker layer of soil that holds most of the organic matter and plant roots. Screened topsoil is sold in bulk by the cubic yard and in bags by volume or weight. It is a growing medium, so the depth you choose depends on what will grow in it.

This tool is not for surface cover. A 2 to 4 inch layer of bark belongs in the mulch calculator, and sand for a sandbox or base belongs in the sand calculator, which works in tons.

The calculator multiplies the area by the depth, adds your settling allowance, then keeps only the topsoil share of the mix.

1. Area. Length x width for a rectangle, or pi x radius squared for a circle.
2. Volume. Area x depth, with inches divided by 12 or centimeters divided by 100.
3. Settling and mix. The volume is multiplied by 1 plus your allowance, then by the topsoil share. A 1:1 blend with compost uses a 50 percent share.
4. Buying units. Cubic feet divide by 27 to give cubic yards. Bags are the volume divided by the bag size, rounded up.

The 324 comes from 27 cubic feet x 12 inches: one cubic yard covers 324 square feet at 1 inch deep.

New lawn. A 50 ft x 20 ft lawn is 1,000 sq ft. At 6 in it needs 500 cu ft, or 18.52 cu yd. At $35 a cubic yard, that is $648.15 before delivery.

Raised bed. An 8 ft x 4 ft bed filled 12 in deep holds 32 cu ft. With a 10 percent settling allowance, that is 35.2 cu ft, or 24 bags of 1.5 cu ft. At $8.50 a bag, the soil costs $204.00.

Blended bed. A 10 ft x 5 ft bed at 6 in needs 25 cu ft of mix, or 0.93 cu yd (0.71 cubic m). With a 50 percent topsoil share, you buy 0.46 cu yd of topsoil and 0.46 cu yd of compost.

Metric bed. A 2 m x 1 m bed at 30 cm holds 0.6 cubic m. With 10 percent settling, that is 660 L, or 14 bags of 50 L.

Depth drives the answer, and settling decides how much you top up later.

What You Are Growing

New Mexico State University calls 4 inches of soil the absolute minimum for a lawn and recommends 6 inches or more for deep roots. For raised beds on hard surfaces, University of Maryland Extension suggests at least 8 inches for leafy greens, beans and cucumbers, and 12 to 24 inches for peppers, tomatoes and squash.

Settling

Loose soil settles after rain and watering, and organic matter breaks down. Illinois Extension calls settling a fact of raised bed gardening and says a few inches of compost or topsoil each year keeps up with it. The settling field lets you add your own margin, since no single percentage fits every soil.

The Mix

University of Maryland Extension suggests compost and topsoil at 1:2 or 1:1 on top of a bed. For beds on hard surfaces at least 16 inches deep, it limits topsoil to 20 percent by volume. Set the topsoil share to match your recipe.

Existing Soil

Measure how much good soil is already there. A lawn that has 2 inches of usable soil needs only 2 more to reach the 4 inch minimum.

Moisture and Weight

USDA NRCS lists ideal dry bulk densities below 1.40 grams per cubic centimeter for loams and below 1.60 for sands. Moist soil in a truck or bag weighs more than that dry figure, so treat the weight result as a rough guide.

Bags suit small beds and top-ups, while bulk usually costs less per cubic yard once a job needs a delivery.

Enter both in the calculator to compare. Price the bags first, then switch to Bulk and add the delivery charge to the price per cubic yard.

New Lawns from Seed or Sod

Choose New lawn. The verdict checks your depth against the NMSU 4 inch minimum and 6 inch recommendation. The mulch or topsoil guide explains which material fits which job.

Raised Beds and Vegetable Gardens

Choose Raised bed, add settling, and set a compost share if you blend. The raised bed soil guide walks through bed sizes and bag counts.

Fill and Levelling

For low spots and grading, enter the average depth. Spread the soil in layers and firm each one before you measure again.

1. Using Inches as Feet

A 1,000 sq ft lawn times 6 gives 6,000, which reads as 6,000 cubic feet. The depth must be 0.5 ft, which gives 500 cubic feet.

2. Ordering Cubic Feet as Cubic Yards

One cubic yard is 27 cubic feet. Mixing them up means ordering 27 times too much, or too little.

3. Forgetting Settling in Raised Beds

A bed filled level with the top will sink after the first watering. Plan a margin now, or plan to top up.

4. Buying Weight Bags Without Checking Volume

A 40 lb bag of damp soil holds less soil than a 40 lb bag of dry soil. Compare bags by the volume printed on them where you can.

5. Filling a Deep Bed with Topsoil Alone

For beds on hard surfaces, UMD limits topsoil to 20 percent by volume. Heavy soil alone can drain poorly in a tall bed.

The volume is exact for the size and depth you enter. Settling and weight depend on your soil, so they are estimates.

One cubic yard covers 324 square feet at 1 inch, 81 square feet at 4 inches and 54 square feet at 6 inches. Divide 324 by your depth in inches.

New Mexico State University gives 4 inches as the absolute minimum and recommends 6 inches or more for deep roots, measured after firming.

Multiply length, width and depth. An 8 by 4 foot bed at 12 inches holds 32 cubic feet, or about 1.19 cubic yards, before any settling allowance.

It depends on moisture and texture. At the 1,400 kg per cubic meter used here, a cubic yard weighs about 1,070 kg, or 2,360 lb. Wet soil weighs more.

You need 27 bags of 1 cubic foot, 18 bags of 1.5 cubic feet or 13.5 bags of 2 cubic feet.

For raised beds, University of Maryland Extension suggests adding compost and topsoil at a 1:2 or 1:1 ratio. Set the topsoil share to 67 or 50 percent to match.

There is no single figure. Illinois Extension notes that beds settle every year and a few inches of top-dressing keeps up, so enter a margin you are comfortable with.

No. Fill dirt is mostly subsoil for raising grade, and garden soil is often topsoil blended with compost. The volume math is the same for all three.

Suppliers may round to whole or half yards, or assume the soil will be firmed. Ask whether their figure is loose or compacted.

No. The calculation runs in your browser and nothing is sent to our servers. Anything you choose to Save stays in this browser only.

• Turfgrass establishment: 4 inch minimum and 6 inch recommended soil depth (New Mexico State University, Cooperative Extension Guide H-509).
• Soil to fill raised beds: depths, compost ratios and topsoil share (University of Maryland Extension).
• Refreshing raised bed soil: settling and yearly top-dressing (University of Illinois Extension).
• Urban soil compaction: ideal bulk densities by soil texture (USDA NRCS Soil Quality Urban Technical Note No. 2).
• NIST Handbook 44, Appendix C: cubic foot and cubic yard (National Institute of Standards and Technology).