How this calculator works
Topsoil is sold by volume. Multiply the area by the depth in metres to get cubic metres, add an allowance for it settling, and for bags divide by the size of a bag in cubic metres: a 50 litre bag is 0.05 m³, so there are 20 to the cubic metre.
Worked example: a 5 × 4 m lawn (20 m²) topped up with 100 mm: 20 × 0.1 = 2 m³, or 2.2 m³ with 10% for settling. That weighs about 3.1 tonnes, and is 44 bags of 50 litres.
How far does 1 m³ of topsoil go?
Area covered by one cubic metre at each depth, and the bags of 50 litres in a cubic metre.
| Depth | Area per m³ | Use |
|---|---|---|
| 25 mm | 40.0 m² | Topping up a lawn |
| 50 mm | 20.0 m² | Levelling a lawn |
| 100 mm | 10.0 m² | Sowing or turfing |
| 150 mm | 6.7 m² | New beds |
| 300 mm | 3.3 m² | Raised beds |
Tips before you buy
- Loose topsoil delivered in bulk (a bag of about a cubic metre, or a loose load) is much cheaper than small bags for anything over a few cubic metres.
- Rake the surface so that it is even and fine, firm it by treading, and let it settle for a few days before sowing or turfing.
- Do not bury a lawn or the base of a tree under a deep layer of fresh soil. Keep it away from the trunks and from the damp-proof course of a house, which should stay at least 150 mm above the soil.
- Cheap topsoil can contain weeds, stones and clay. Ask for screened topsoil to BS 3882 if you can.
- For raised beds, a mix of topsoil, compost and some grit usually beats straight topsoil.
Tools & materials for this project
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Frequently asked questions
How much topsoil do I need for a 5m x 4m lawn?
For 100 mm deep, 2.2 m³ with 10% extra (3.1 tonnes), which is 44 bags of 50 litres. For a 50 mm top-up, half that.
How many bags of topsoil make a cubic metre?
20 bags of 50 litres, 28.6 bags of 35 litres or 40 bags of 25 litres.
How much does a cubic metre of topsoil weigh?
About 1.4 tonnes, ranging from about 1.2 tonnes when dry to 1.6 tonnes when wet.
How deep should topsoil be for a new lawn?
At least 100 mm on top of well-loosened ground, and 150 mm if the soil beneath is poor. For a lawn that is already there, a 25 to 50 mm top dressing will do.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.