Topsoil Calculator
Work out how much topsoil to buy for lawns and beds, with volume, bag quantities and optional material cost.
- Extra allowance: 0%. Applied once to the combined volume.
- Bag capacity: —. Bag quantities are rounded up after combining all areas.
- Supplier density: —. Tonnage is an estimate.
- Price used: —.
Volume is based on the dimensions entered. Check soil suitability, required depth and any settlement allowance with your supplier. Bag costs use whole bags; loose-soil costs use the calculated quantity. Supplier minimum orders and delivery charges are not included.
Use this topsoil calculator to work out how much topsoil to buy for lawns and beds. Calculate volume, whole bags or estimated tonnes, with an optional material cost using your supplier’s prices.
PRO TIP: Check delivery access and where the soil will be unloaded before choosing loose soil or bulk bags. Moving soil from a kerbside drop to the garden can be a substantial part of the job.
How to use this topsoil calculator
- Use metres and millimetres in Metric mode, or feet and inches in Imperial mode. For a circle, measure the diameter across the centre. For an L-shaped space, use Add another area to enter separate rectangles without overlaps.
- For other shapes, select I know the area and enter the net area after subtracting paths or beds you will not cover. Each area can have its own depth. Enter only the thickness of soil you are adding; 10 cm is 100 mm.
- Choose your buying method. For bags, enter the supplier’s litres per bag; for tonnes, enter their density in tonnes/m³. Add a price only if you want a cost estimate, matching Price based on to the quote.
Understanding your results
Use Topsoil to Buy as your ordering guide. Bag quantities are rounded up after combining all areas; Extra from bag rounding is additional to your chosen allowance. Bag costs use whole bags, while loose-soil costs use the calculated volume or estimated weight. If you’re preparing the area for a new lawn, use our turf calculator to work out how many rolls to order.
How the Maths Works
Volume (m³) = area (m²) × depth (mm) ÷ 1,000. The calculator adds your percentage allowance to the combined volume. It then divides litres by bag capacity and rounds up, or multiplies cubic metres by supplier density to estimate tonnes.
Example: 5 m × 4 m × 100 mm = 2 m³ (2,000 litres). With 5% extra, this becomes 2.1 m³: three 800-litre bags, supplying 2.4 m³ in total.
Common Mistakes to Avoid
- Do not assume a bulk bag contains one cubic metre or weighs one tonne. Use the listed volume; if only weight is given, ask the supplier for its volume.
- Do not add the same settlement allowance twice. If your supplier has already increased the recommended depth to account for settlement, check before adding a further percentage.
faqs
How much area does one cubic metre cover?
Before allowance, 1 m³ covers 20 m² at 50 mm deep, 10 m² at 100 mm, or 6.67 m² at 150 mm. These are coverage examples, not recommended depths.
How much does a cubic metre of topsoil weigh?
There is no fixed weight: moisture and soil composition affect density. For an order priced by tonne, use the supplier’s density for that product rather than assuming 1 m³ equals 1 tonne.
disclaimer
This is a quantity estimate, not a soil specification. Confirm suitability and final order quantities with your supplier. Delivery, labour and supplier minimum orders are excluded from the cost; VAT is included only if it is included in the price you enter.