Mulch Topsoil Calculator
Enter the area and depth to see how much topsoil, garden soil or fill dirt you need in cubic feet, cubic yards and bags. It uses the same volume math as our mulch calculator.
Key takeaways
- Cubic yards of topsoil = area (sq ft) × depth (in) ÷ 324.
- 1 cubic yard = 27 cu ft = 27 bags of 1 cu ft, 36 bags of 0.75 cu ft, 18 of 1.5 cu ft or 13.5 of 2 cu ft.
- 100 sq ft at 4 inches needs 33.3 cu ft (1.23 yd³) before any settling margin.
- Add around 10–20% for fill jobs, because loose soil settles.
- For a new lawn, Illinois Extension sets a goal of six inches or more of well-prepared soil.
Topsoil formula
Cubic yards = area (sq ft) × depth (in) ÷ 324. For bags, divide the cubic feet (area × depth ÷ 12) by the bag volume and round up. Example: a 20 × 10 ft bed filled 4 inches deep is 200 × 4 ÷ 12 = 66.67 cu ft = 2.47 cubic yards, or 67 bags of 1 cu ft.
Topsoil per 100 sq ft
| Depth | Cu ft | Cu yd | 0.75 cu ft bags | 1 cu ft bags | 1.5 cu ft bags | 2 cu ft bags |
|---|---|---|---|---|---|---|
| 1 in | 8.33 | 0.31 | 12 | 9 | 6 | 5 |
| 2 in | 16.67 | 0.62 | 23 | 17 | 12 | 9 |
| 3 in | 25 | 0.93 | 34 | 25 | 17 | 13 |
| 4 in | 33.33 | 1.23 | 45 | 34 | 23 | 17 |
| 6 in | 50 | 1.85 | 67 | 50 | 34 | 25 |
Multiply by 2 for 200 sq ft, by 5 for 500 sq ft and so on (then round the bag count up).
Why add extra for soil?
Loose soil settles after it is watered and walked on, and bulk deliveries are measured loose. Many gardeners add around 10–20% for fill jobs; for a thin top-dressing a smaller margin is usually enough. Set the percentage that suits your project in the calculator.
Bags or bulk?
Soil is heavy, so the bag-versus-bulk decision tips toward bulk sooner than with mulch. The break-even math is the same as in our bagged vs bulk mulch guide: compare the yard price plus delivery with the cost of the equivalent number of bags (27 bags of 1 cu ft per yard).
Finishing the bed with mulch afterwards? Use the mulch calculator and the step-by-step guide for odd shapes.
Worked examples with the math
Filling a 4 × 8 ft raised bed 12 inches deep. Area = 4 × 8 = 32 sq ft. Volume = 32 × 12 ÷ 12 = 32 cu ft = 32 ÷ 27 = 1.19 cubic yards. With 10% extra for settling that is 35.2 cu ft, so buy 36 bags of 1 cu ft or 18 bags of 2 cu ft. If the bed already holds a few inches of old soil, measure the empty depth and enter that instead.
Spreading 4 inches over a 1,000 sq ft lawn area. 1,000 × 4 ÷ 324 = 12.35 cubic yards. With 10% extra: 13.58 yd³. Most suppliers sell bulk soil in whole or half yards, so you would order 14 yards. That is a bulk-delivery job: in 1 cu ft bags it would be about 367 bags.
Filling a round low spot. A dip about 8 ft across and 3 inches deep on average: area = 3.1416 × 4² = 50.3 sq ft, volume = 50.3 × 3 ÷ 12 = 12.57 cu ft (0.47 yd³), or 13 bags of 1 cu ft. For dips, measure the depth at several points and average them, since the center is deeper than the edges.
Bags per cubic yard of soil
| Bag size | Bags per cubic yard | Bags per 100 sq ft at 2 in | Bags per 100 sq ft at 6 in |
|---|---|---|---|
| 0.75 cu ft | 36 | 23 | 67 |
| 1 cu ft | 27 | 17 | 50 |
| 1.5 cu ft | 18 | 12 | 34 |
| 2 cu ft | 13.5 | 9 | 25 |
Some potting mixes and garden soils are labeled in quarts rather than cubic feet. One cubic foot is about 25.7 US dry quarts, so divide the quarts on the label by 25.7 to get cubic feet before using the calculator.
How deep should topsoil be?
It depends on the job. For a new lawn, University of Illinois Extension says “a goal is to have six inches or more of well prepared soil” and recommends amending the soil to a depth of 6 to 8 inches according to a soil test. That is a target for the finished soil profile, not the amount you must import: if you already have 3 inches of decent soil, you only need to add the difference. Raised beds are filled to their full height, and leveling low spots only needs the depth of the dip.
When you regrade near the house, the same Illinois guide says final slopes should be one to two percent away from buildings (a 1 to 2 ft drop per 100 ft). Keep that in mind before piling soil against a foundation.
Common topsoil mistakes
- Mixing up inches and feet. The calculator asks for depth in inches. Entering 1 for “one foot” gives you one-twelfth of the soil you need; enter 12.
- Skipping the settling margin. Loose soil compacts once it is watered and walked on, so a bed filled exactly level will sit lower a few weeks later.
- Rounding bags down. Always round bag counts up. The calculator does this for you.
- Measuring only the longest side. For L-shaped or curved areas, split the area into simple shapes or average several widths, as shown in our guide to calculating odd shapes.
Frequently asked questions
How many bags of topsoil are in a cubic yard?
A cubic yard is 27 cu ft, so it equals 27 bags of 1 cu ft, 36 bags of 0.75 cu ft, 18 bags of 1.5 cu ft or 13.5 bags of 2 cu ft.
How much topsoil do I need for 1,000 square feet?
At 2 inches deep you need 1,000 × 2 ÷ 324 = 6.17 cubic yards (166.7 cu ft). At 4 inches you need 12.35 cubic yards. Add 10–20% for settling on fill jobs.
How much soil does a 4 x 8 raised bed need?
A 4 × 8 ft bed filled 12 inches deep needs 32 cu ft, or 1.19 cubic yards. With 10% extra that is 35.2 cu ft, or 36 bags of 1 cu ft.
How deep should topsoil be for a new lawn?
University of Illinois Extension sets a goal of six inches or more of well-prepared soil and recommends amending to a depth of 6 to 8 inches based on a soil test. Subtract the good soil you already have to find how much to add.
Can I use the mulch calculator for topsoil?
Yes. The volume math is identical: area × depth ÷ 12 gives cubic feet and ÷ 27 gives cubic yards. This page simply offers the smaller bag sizes soil is sold in and a higher default settling margin.