Cubic Feet Calculator
Work out cubic feet from three sizes, in feet, inches, metres or cm. Then see what that space holds in m³, litres and tonnes.
Measure the space
Your answer
1.13 m³ · 1,133 litres · 1.48 cubic yards
What it weighs
- MOT Type 12.36 tonnes
- Crusher run2.06 tonnes
- Ballast1.87 tonnes
- Gravel (20 mm)1.81 tonnes
- Slate chippings1.81 tonnes
- Sharp or building sand1.71 tonnes
- Tarmac (laid)2.66 tonnes
- Sand and cement screed, set and dry (Tarmac)2.38 tonnes
- Topsoil0.91 tonnes
- Bark0.28 tonnes
Tonnes for UK materials as laid, from bag sizes and cover. Wickes says wetness can change the weight of its ballast by about 5%.
Quick answers
- The sum
- Length × width × height, all in feet, gives cubic feet.
- Sizes in inches
- Divide each one by 12 first. Or multiply the inches, then divide by 1,728.
- 1 cubic foot
- About 28.3 litres, or 0.0283 m³.
- Cubic metres and yards
- 1 m³ is about 35.3 cubic feet. 1 cubic yard is exactly 27 cubic feet.
How to work it out
- Measure the length, width and height (or depth) of the space.
- Change any inches to feet: divide by 12. Change metres to feet: divide by 0.3048.
- Multiply length × width × height. The answer is in cubic feet.
- To get m³, multiply the cubic feet by 0.0283.
6 in ÷ 12 = 0.5 ft
10 × 8 × 0.5 = 40 cubic feet
40 × 0.0283 = 1.13 m³
How to calculate cubic feet from feet and inches
Finding cubic feet takes three sizes. Depth is sometimes in inches. Change any inches to feet before you multiply.
| Depth | In feet | Cubic feet for 10 sq ft | Cubic feet for 100 sq ft |
|---|---|---|---|
| 1 in | 0.083 | 0.83 | 8.3 |
| 2 in | 0.167 | 1.67 | 16.7 |
| 3 in | 0.25 | 2.5 | 25 |
| 4 in | 0.333 | 3.33 | 33.3 |
| 6 in | 0.5 | 5 | 50 |
| 9 in | 0.75 | 7.5 | 75 |
| 12 in | 1 | 10 | 100 |
If all three sizes are in inches, multiply them as they are. Then divide by 1,728, the cubic inches in one cubic foot.
Cubic feet from metres, litres and yards
A foot is exactly 0.3048 m. So a metre is about 3.28 feet, and a cm is about 0.0328 feet.
| Unit | In 1 cubic foot | One of them is |
|---|---|---|
| Litres | 28.32 | 0.0353 cubic feet |
| Cubic metres (m³) | 0.0283 | 35.31 cubic feet |
| Cubic yards | 0.037 | 27 cubic feet |
| Cubic inches | 1,728 | 0.000579 cubic feet |
Measured in metres? Work out m³ first, then multiply by 35.31. The calculator above does this for you.
What a cubic foot of gravel, sand or soil weighs
Stone, sand and soil are sold by weight or by the bag. These weights come from UK bag sizes and the cover printed on them.
| Material | Weight | Cubic feet per tonne |
|---|---|---|
| Tarmac (laid) | 67 kg | 15.0 |
| Sand and cement screed, set and dry (Tarmac) | 59 kg | 16.8 |
| MOT Type 1 | 59 kg | 17.0 |
| Crusher run | 52 kg | 19.4 |
| Ballast | 47 kg | 21.4 |
| Gravel (20 mm) | 45 kg | 22.1 |
| Slate chippings | 45 kg | 22.1 |
| Sharp or building sand | 43 kg | 23.4 |
| Topsoil | 23 kg | 44.1 |
| Bark | 7 kg | 141.3 |
Wickes says wetness can change the weight of its ballast by about 5%.
To get kg, multiply your cubic feet by the weight in the middle column.
UK bags in litres, as cubic feet
Garden soil and bark are sold in litres in the UK. Here are some common bag sizes from Wickes and B&Q.
| Bag | What it is | Cubic feet |
|---|---|---|
| 25 litres | small bag of topsoil | 0.88 |
| 100 litres | large bag of bark | 3.53 |
| 500 litres | bulk bag of topsoil or bark | 17.66 |
To find how many bags fill a space, divide the cubic feet by the bag's cubic feet. Round up to a whole bag.
Round shapes and easy mistakes
A round planter or hole
Halve the width across to get the radius. Then multiply radius × radius × 3.14 × depth, all in feet.
A planter 2 ft across and 1.5 ft deep holds about 4.7 cubic feet.
Mistakes to check
- Inches left as inches. 6 in is 0.5 ft, not 6. Miss this and the answer is 12 times too big.
- Square feet are not cubic feet. Square feet is a flat area. Cubic feet adds the depth.
- Mixed units. Use feet for all three sizes, or metres for all three.
Questions people ask
How do you calculate cubic feet?
Multiply the length, width and height, all in feet. A space 10 ft long, 8 ft wide and 0.5 ft deep is 40 cubic feet.
How do I calculate cubic feet from inches?
Multiply the three sizes in inches, then divide by 1,728. A box 24 × 18 × 12 in is 5,184 cubic inches. That is 3 cubic feet.
How do I find cubic feet from metres?
Multiply the sizes in metres to get m³. Then multiply by 35.31. A box 2 × 1 × 0.5 m is 1 m³, or about 35.3 cubic feet.
How do I convert cubic feet to cubic metres?
Multiply by 0.0283. So 40 cubic feet is about 1.13 m³.
How many litres are in a cubic foot?
About 28.32 litres. A foot is exactly 0.3048 m, so the figure never changes.
How many cubic feet are in a cubic yard?
27. A cubic yard is 3 feet long, 3 feet wide and 3 feet high. That makes 3 × 3 × 3 = 27.
How much does a cubic foot of gravel weigh?
About 45 kg for 20 mm gravel, at 1.6 tonnes per m³. That weight comes from a Wickes bulk bag and its cover.
How many cubic feet is a 100 litre bag?
About 3.53 cubic feet. Divide litres by 28.32 to get cubic feet.
Where our numbers come from
- Unit sizes: NIST Handbook 44, Appendix C (1 ft = 0.3048 m; 1 US gallon = 231 cubic inches)
- Type 1 weight and price: Wickes 800 kg bag (checked Oct 2026)
- Crusher run weight: Greenvale Products (1 tonne covers about 11 m² at 50 mm)
- Ballast weight: Wickes ballast bulk bag (800 kg covers 9.7 m² at 50 mm)
- Gravel weight: Wickes UK 20 mm gravel bulk bag (800 kg covers 20 m² at 25 mm)
- Slate weight: Wickes 20 mm slate chippings bulk bag
- Sand weight: Wickes sharp sand bulk bag (800 kg covers 10.6 m² at 50 mm)
- Asphalt weight: Asphalt Institute (110 lb per square yard per inch)
- Tarmac coverage: Heidelberg Materials asphalt calculator (14–18 m² per tonne at 25 mm)
- Screed: Tarmac Truscreed data sheet (weight once dry; thickness over underfloor heating)
- Topsoil weight: Wickes 500 litre topsoil bag (about 400 kg)
- Bark weight: Wickes 500 litre bark bag (about 125 kg)
- Topsoil 25 L bag covers 0.5 m²: B&Q Verve
- Topsoil bag prices: Wickes 25 L and 500 L bags
- Bark 100 L bag: B&Q Verve (4 m² at 25 mm)
- Bark bag prices: Wickes 100 L and 500 L bags
Made by BuildersCount. Last checked 4 Oct 2026.
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