How Many Cubic Feet Is a 40 lb Bag of Topsoil?

The Short Answer

A 40 lb bag of topsoil holds about 0.75 cubic feet for typical moist bagged topsoil, which equals about 21 litres. That figure uses a density of 53 lb per cubic foot. The full range is 0.73 to 0.80 cubic feet, because bagged topsoil usually weighs 50 to 55 lb per cubic foot.

About 36 bags make one cubic yard at that midpoint density. The buyable range is 34 to 38 bags, because the exact count moves with density. Weight alone does not tell you volume. Density does.

Use the Calculator Before You Buy

Use the Topsoil Weight to Cubic Feet Calculator to convert any bag weight to volume. Enter weight in lb and it shows volume and bags per cubic yard, using the same formula and density range as this blog. For a full bed, use the Topsoil Calculator.

The Formula That Controls the Answer

Volume equals weight divided by bulk density. Weight is the number printed on the bag. Bulk density is the weight of one cubic foot of that soil.

For a 40 lb bag at 53 lb per cubic foot, the maths is 40 divided by 53, which equals 0.75 cubic feet. The exact result is 0.7547 cubic feet. The reverse formula is weight equals volume times bulk density. A 1.5 cubic foot bag at 53 lb per cubic foot weighs 1.5 times 53, which equals 79.5 lb, shown as about 80 lb. Site density is 50 to 55 lb per cubic foot, which equals 0.8 to 0.9 tonnes per cubic metre.

Bag Volume by Density

This table shows what a 40 lb bag holds at each end of the site range and at the midpoint.

Density in lb per cubic foot	Volume of a 40 lb bag in cubic feet	Volume in litres	Exact bags per cubic yard	Buyable bags per cubic yard
50	0.80	22.6	33.75	34
53	0.75	21.2	36.00	36
55	0.727	20.6	37.13	38

Litres use 1 cubic foot equals 28.3 litres, so 0.75 times 28.3 equals 21.2 litres. Bag counts use 1 cubic yard equals 27 cubic feet, so 27 divided by 0.80 equals 33.75 bags exact and 34 bags buyable, while 27 divided by 0.727 equals 37.13 bags exact and 38 bags buyable. Always round up.

Why 27 Bags, 36 Bags and 54 Bags All Appear Online

Each count comes from a different density, and most pages do not state the density they used.

The 36 bag answer comes from site bagged density. A 40 lb bag at 53 lb per cubic foot holds 0.75 cubic feet. Divide 27 cubic feet in a cubic yard by 0.75 and you get 36 bags. That is the correct planning figure for typical moist bagged topsoil, with a buyable range of 34 to 38 bags.

The 54 bag answer comes from bulk dense density. A 40 lb bag at 80 lb per cubic foot holds 0.50 cubic feet, because 40 divided by 80 equals 0.50. Divide 27 by 0.50 and you get 54 bags. That arithmetic is correct for 80 lb per cubic foot, but that is not bagged damp topsoil.

The 27 bag answer comes from a density of 40 lb per cubic foot. A 40 lb bag at 40 lb per cubic foot holds 1.0 cubic feet, because 40 divided by 40 equals 1.0. Divide 27 by 1.0 and you get 27 bags. That density is below the site range, so the count is too low.

Worked Examples You Can Copy

One cubic yard needs 36 bags at the midpoint. At the low end, 27 divided by 0.80 equals 33.75 bags exact, so 34 bags buyable. At the high end, 27 divided by 0.727 equals 37.13 bags exact, so 38 bags buyable.

A bed 4 feet by 8 feet at 11 inches deep needs 4 times 8 times 11 divided by 12, which equals 29.33 cubic feet. Divide 29.33 by 0.75 to get 39.11 bags exact, so 40 bags buyable from the unrounded volume. Check a full bed with the Garden Volume Calculator and the Soil Calculator.

For lifting, 36 bags times 40 lb equals 1440 lb per cubic yard at the midpoint. Use that total to plan trips.

Bags per Cubic Yard by Bag Size

Use the volume printed on the bag when it is printed. That volume controls the count.

Bag volume in cubic feet	Volume in litres	Exact bags per cubic yard	Buyable bags per cubic yard
0.75	21.2	36.00	36
1.00	28.3	27.00	27
1.50	42.5	18.00	18
2.00	56.6	13.50	14

A 2 cubic foot bag holds 56.6 litres, because 2 times 28.3 equals 56.6. For one cubic yard, 27 divided by 2 equals 13.5 bags exact, so 14 bags buyable. Never present 13.5 bags as a buyable count.

Moisture Changes the Answer

Dry soil can be 30 percent lighter than moist soil. That is the only moisture figure verified for this blog, so use it as an illustration only. At 53 lb per cubic foot moist, dry soil at 30 percent lighter weighs 53 times 0.70, which equals 37.1 lb per cubic foot. A 40 lb bag of that dry soil would hold 40 divided by 37.1, which equals 1.08 cubic feet, larger than the moist figure of 0.75 cubic feet. Bag labels may state volume before compression, so loosen settled soil before you measure it.

Topsoil and Potting Mix Weigh Different Amounts

For topsoil, a 1.5 cubic foot bag weighs 60 to 80 lb. At site density, 1.5 times 50 equals 75 lb and 1.5 times 55 equals 82.5 lb, so the site range is wider at the low end to cover drier topsoil. For potting mix, the same size weighs 20 to 40 lb. That implies a density of 13.3 to 26.7 lb per cubic foot, from 20 divided by 1.5 and 40 divided by 1.5. Potting mix is much lighter because it holds more air and light organic matter. Do not use a topsoil weight for a potting mix bag, or the reverse.

Litres and Cubic Metres for Metric Orders

Use 1 cubic foot equals 28.3 litres, 1 cubic yard equals 27 cubic feet, and 1 cubic metre equals 1000 litres, which equals 35.3 cubic feet. A 40 lb bag at the midpoint holds 21.2 litres, shown as 21 litres.

For small metric bags, 1 cubic metre needs 40 bags of 25 litres, because 1000 divided by 25 equals 40. It needs 34 bags of 30 litres rounded up, because 1000 divided by 30 equals 33.33. For weight, site density equals 0.80 to 0.88 kg per litre. At that density, 25 litres weighs 20.0 to 22.0 kg and 1 cubic metre weighs 800 to 880 kg.

How to Read the Bag Label

Read volume first. The volume printed on the bag controls the bag count for a cubic yard. Weight printed on the bag does not control volume. First, look for volume in cubic feet or litres. If it shows 0.75 cubic feet, use 36 bags per cubic yard. If it shows 1.5 cubic feet, use 18 bags. If it shows 2 cubic feet, use 14 bags buyable. Second, look for weight in lb. If it shows 40 lb and no volume, use the formula in this blog and the density range.

Common Mistakes to Avoid

1. Using a single fixed number without stating density. Give the range 0.73 to 0.80 cubic feet.
2. Copying 54 bags per cubic yard for bagged topsoil. That count uses 80 lb per cubic foot, which is bulk dense density.
3. Copying 27 bags per cubic yard for bagged topsoil. That count uses 40 lb per cubic foot, below site density.
4. Presenting 13.5 bags as a buyable count for a 2 cubic foot bag. The buyable count is 14 bags.
5. Using a topsoil weight for potting mix, or the reverse. Topsoil is 60 to 80 lb for 1.5 cubic feet.
6. Using a bulk yard weight to plan a bag order. At the midpoint, 36 bags times 40 lb equals 1440 lb per cubic yard.
7. Rounding down a bag count. Always round up, because a shortfall leaves a bed low.
8. Trusting a volume figure with no density stated. Ask for the density, then divide weight by density to get volume.

How to Buy the Right Amount

Start with the volume you need in cubic feet. Use the Soil Calculator or the Garden Volume Calculator to work out that volume from length, width and depth. Then divide that volume by the volume of one bag. Use 0.75 cubic feet per 40 lb bag as the midpoint. Round the result up. For one cubic yard, that gives 36 bags, with a range of 34 to 38 bags. For half a cubic yard, which equals 13.5 cubic feet, divide 13.5 by 0.75 to get 18 bags exact. For two cubic yards, divide 54 by 0.75 to get 72 bags exact.

Frequently Asked Questions

Q: How many cubic feet is a 40 lb bag of topsoil?
A: About 0.75 cubic feet, about 21 litres, range 0.73 to 0.80 cubic feet at 50 to 55 lb per cubic foot.

Q: How many 40 lb bags of topsoil make a cubic yard?
A: About 36 bags at 53 lb per cubic foot, buyable range 34 to 38 bags.

Q: Why do some sites say 54 bags per cubic yard?
A: They use bulk dense density of 80 lb per cubic foot, where a 40 lb bag holds 0.50 cubic feet.

Q: How much does a 1.5 cubic foot bag of topsoil weigh?
A: Around 60 to 80 lb for topsoil, and 20 to 40 lb for potting mix in the same size.

Q: How many litres is a 40 lb bag of topsoil?
A: About 21 litres at the midpoint, from 0.75 times 28.3, which equals 21.2 litres.

Q: Does dry topsoil hold more volume for the same weight?
A: Yes, as an illustration only. Dry soil can be 30 percent lighter, so a 40 lb bag of dry soil would hold 1.08 cubic feet.