Topsoil Calculator
With length 20 ft, width 8 ft, depth 6 in, bag size 1.5 cu ft and 1 more field, topsoil comes to 3.41 cu yd — topsoil needed. It is reached in 8 steps, the last of which is 92 / 27, and each one is printed on the page with its numbers filled in. The formula is the one published by USDA NRCS, not an approximation fitted to it.
How much topsoil a bed or a lawn needs, in cubic yards and in bags, with the weight — the number that decides truck or car boot.
Formula and sources checked · How we check
Length 20 ft, Width 8 ft, Depth 6 in, Bag size 1.5 cu ft
3.41 cu yd
Topsoil needed for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Volume
20 * 8 * 0.580 cu ft- With the settling allowance
80 * (1 + 15 / 100)92 cu ft- Cubic yards to order
92 / 273.407 cu yd- Bags, if buying bagged
ceil(92 / 1.5)62- Weight, dry
3.4074074 * 22007,496.296 lb- Weight in tons, dry
7496.2963 / 20003.748 tons- Weight if wet
3.4074074 * 2800 / 20004.77 tons- Half-ton pickup loads
ceil(3.7481481 / 0.5)8
Worked example
A 20 by 8 ft bed at 6 inches deep is 80 cubic feet, and 92 with a 15% settling allowance — 3.41 cubic yards. That is 62 bags at 1.5 cubic feet each, or a delivery: 3.75 short tons dry and up to 4.8 wet, which is eight trips in a half-ton pickup and one in a truck.
How to work it out yourself
- 1.Order by volume and plan by weight. Soil is sold by the cubic yard and moved by the ton, and a yard of wet topsoil is 1.4 tons — more than a half-ton pickup should carry, whatever fits in the bed.
- 2.Add the settling allowance rather than rounding up at the end. Bulk soil arrives loose and loses 10-20% of its volume in the first weeks, which is why a bed filled exactly level ends up dished.
- 3.Cross the bag-or-bulk line deliberately. Bagged soil costs three to five times as much per cubic yard, and the crossover is usually around one cubic yard — under that the delivery fee dominates, over it the bags do.
How far one cubic yard goes
A cubic yard is 27 cubic feet. Spread one inch deep it covers 324 square feet, and every other depth is that figure divided by the depth in inches — which is the whole table in one sentence.
| Depth | Square feet | Square yards |
|---|---|---|
| 1 in | 324 | 36.0 |
| 2 in | 162 | 18.0 |
| 3 in | 108 | 12.0 |
| 4 in | 81 | 9.0 |
| 6 in | 54 | 6.0 |
| 8 in | 41 | 4.5 |
| 10 in | 32 | 3.6 |
| 12 in | 27 | 3.0 |
Cubic yards for a given area
| Area | 1 in | 2 in | 3 in | 4 in | 6 in | 8 in | 10 in | 12 in |
|---|---|---|---|---|---|---|---|---|
| 100 sq ft | 0.31 | 0.62 | 0.93 | 1.23 | 1.85 | 2.47 | 3.09 | 3.70 |
| 200 sq ft | 0.62 | 1.23 | 1.85 | 2.47 | 3.70 | 4.94 | 6.17 | 7.41 |
| 500 sq ft | 1.54 | 3.09 | 4.63 | 6.17 | 9.26 | 12.35 | 15.43 | 18.52 |
| 1,000 sq ft | 3.09 | 6.17 | 9.26 | 12.35 | 18.52 | 24.69 | 30.86 | 37.04 |
Suppliers deliver in whole or half yards, so round up — a truck will not bring 2.37.
Bags to the cubic yard
| Bag | Holds | Bags per yard |
|---|---|---|
| Mulch, 2 cu ft bag | 2 cu ft | 14 |
| Mulch, 3 cu ft bag | 3 cu ft | 9 |
| Topsoil or compost, 1 cu ft bag | 1 cu ft | 27 |
| Concrete mix, 80 lb bag | 0.6 cu ft | 45 |
| Concrete mix, 60 lb bag | 0.45 cu ft | 60 |
| Concrete mix, 40 lb bag | 0.3 cu ft | 90 |
Concrete is sold by weight and the yield is printed on the bag, which is why it takes 45 of the 80 lb bags to make a yard rather than the dozen people expect. Past about ten bags, ready-mix is cheaper and far less work.
Depth by use
| Use | Depth | Why |
|---|---|---|
| Mulch, established beds | 2–3 in | Deeper than 3 in holds water against stems and starves roots of air. |
| Mulch, new beds over bare soil | 3–4 in | The extra inch is what suppresses weeds for a season. |
| Topsoil over an existing lawn | 0.25–0.5 in | Any more and the grass underneath is smothered rather than fed. |
| Topsoil for a new lawn | 4–6 in | Roots need the depth once, at the start; it cannot be added later. |
| Gravel walkway | 2–4 in | Over a compacted base, not over soil. |
| Gravel driveway, surface course | 3–4 in | Over 6 to 8 in of compacted base. |
| Gravel driveway, full build | 8–12 in | Base and surface together, laid and compacted in layers. |
| Concrete patio or walkway | 4 in | Four inches is the ordinary residential slab. Follow the specification for anything carrying a vehicle. |
How much extra to order
| Reason | Add | Note |
|---|---|---|
| Compaction, crushed stone | 20% | Six inches loose settles to about five. Order for the finished depth. |
| Settling, mulch and soil | 10–15% | Organic material shrinks as it breaks down over the first season. |
| Spillage and uneven ground | 5–10% | A hole is never the rectangle it was measured as. |
| Concrete, sub-base variation | 5–10% | A slab poured half an inch deep over 200 sq ft is a third of a yard nobody ordered. |
By depth, for this area
| Depth (in) | Topsoil needed | Cubic yards to order | Bags, if buying bagged |
|---|---|---|---|
| 2 | 1.14 cu yd | 1.14 cu yd | 21 |
| 3 | 1.70 cu yd | 1.7 cu yd | 31 |
| 4 | 2.27 cu yd | 2.27 cu yd | 41 |
| 6 | 3.41 cu yd | 3.41 cu yd | 62 |
| 8 | 4.54 cu yd | 4.54 cu yd | 82 |
| 12 | 6.81 cu yd | 6.81 cu yd | 123 |
The formula
- Volume
20 * 8 * 0.5 - With the settling allowance
80 * (1 + 15 / 100) - Cubic yards to order
92 / 27 - Bags, if buying bagged
ceil(92 / 1.5) - Weight, dry
3.4074074 * 2200 - Weight in tons, dry
7496.2963 / 2000 - Weight if wet
3.4074074 * 2800 / 2000 - Half-ton pickup loads
ceil(3.7481481 / 0.5)
Source: USDA NRCS — soil bulk density and its measurement, NIST Handbook 130 — method of sale for soil and mulch, sold by volume
Questions people actually ask
- How much topsoil do I need?
- Length times width times depth, all in feet, divided by 27 for cubic yards — then add 10-20% because bulk soil settles. A 20 by 8 ft bed at 6 inches is 3.41 cubic yards with a 15% allowance, which is 62 bags of 1.5 cubic feet.
- How much does a cubic yard of topsoil weigh?
- About 1.1 short tons dry and up to 1.4 wet — 2,200 to 2,800 lb. That is why a half-ton pickup carries half a yard safely and not the two yards that will physically fit in the bed.
- How deep should topsoil be?
- Six inches for a new lawn or a vegetable bed, three to four for topping up an existing one, and 12 or more where deep-rooted crops go. Under four inches the roots hit whatever is beneath, which is usually the reason the lawn was being replaced.
- Is topsoil sold by weight or by volume?
- By volume, in cubic yards or cubic feet — NIST Handbook 130 makes volume the method of sale for soil and mulch, because the weight moves with the moisture. A yard is a yard whether it rained the night before or not.
Related
- Mulch CalculatorCubic yards and bags of mulch for a bed, with a waste allowance and a warning when the depth would smother the roots.
- Concrete CalculatorCubic yards of concrete for a slab, round pad, footing, column, wall or stairs, with bag counts and cost.
- Square Footage CalculatorSquare footage of a room, wall, border, gable end, ring or triangle from feet-and-inches measurements, with a waste factor and the cost.
- Gravel & Aggregate CalculatorCubic yards and tons of gravel, sand, limestone or topsoil for an area at a given depth.
- Sod CalculatorRolls and pallets of sod for a lawn, from the area and the roll size the farm cuts, with the waste a shaped lawn actually needs.
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