How Much Topsoil Do I Need?

Why Getting the Quantity Right Matters

Ordering too little topsoil means a second delivery — doubling your delivery costs and delaying your project. Ordering too much leaves you with an expensive pile taking up driveway space. Getting the calculation right first time saves money and hassle.

This guide walks through the maths for every common garden project, gives you the depth recommendations you need, and helps you convert your numbers into bulk bags or loose loads.

The Basic Calculation

The formula is straightforward:

Volume (cubic metres) = Length (m) x Width (m) x Depth (m)

For example, if you're laying topsoil over an area 8 metres long and 5 metres wide to a depth of 150mm (0.15m):

8 x 5 x 0.15 = 6 cubic metres

For irregular shapes, break the area into rectangles, calculate each one separately, and add them together.

Depth Recommendations by Project

Different projects need different depths of topsoil. Getting this wrong is the most common mistake — too shallow and your plants won't root properly; too deep and you've wasted money.

New Lawns

For a new lawn from turf or seed, you need 100-150mm of topsoil over the existing ground. Use the deeper end if your subsoil is heavy clay or compacted, and the shallower end if you already have reasonable soil that just needs topping up.

See our full guide on preparing topsoil for a new lawn for the complete process.

Flower Borders and Shrub Beds

Established borders being topped up need 50-75mm. New borders being created from scratch need 150-200mm, especially if you're planting over compacted ground or clay.

Raised Beds

Raised beds need to be filled to within 25-50mm of the top. Most raised beds are 300-450mm deep, so that's how much topsoil you need. For raised beds intended for vegetables, consider filling the bottom third with a cheaper subsoil or rubble for drainage, then topping with quality topsoil. Our guide on the best topsoil for raised beds covers this in detail.

Vegetable Patches

If you're creating a vegetable patch at ground level, aim for 200-300mm of quality topsoil. Vegetables are hungrier than lawn grass and need more root depth, particularly root crops like carrots and parsnips.

Levelling and Filling

If you're filling a depression or levelling a garden, measure the depth at the deepest point and the shallowest, then use the average. Remember that topsoil will settle by roughly 10-15% after it's been laid, so factor that in.

Converting to Bulk Bags and Loose Loads

Bulk Bags

One standard bulk bag (also called a dumpy bag or tonne bag) contains approximately 0.6 cubic metres of topsoil and weighs around 800-1000kg depending on moisture content. A bag is not a full cubic metre — this catches a lot of people out.

To convert your volume to bags: Number of bags = Volume (m³) ÷ 0.6

So 6 cubic metres would need 10 bulk bags.

Loose Loads

For larger projects, a loose load is typically cheaper per cubic metre. Most suppliers deliver loose loads in increments of 1 cubic metre, with minimum orders of 3-5 cubic metres. A standard tipper lorry carries about 14-16 cubic metres.

Small Bags

For tiny projects, 25kg bags from garden centres contain roughly 0.025 cubic metres. You'd need 40 of them to equal one bulk bag — which makes them significantly more expensive per volume. They're only sensible for very small areas.

Practical Tips

• Always order 10% more than your calculation. Topsoil settles, you'll lose some to spillage, and areas always turn out slightly larger than you measured
• Check access before ordering. Bulk bags need a lorry with a crane (HIAB), which needs overhead clearance. Loose loads need a tipper, which needs space to tip. See our guide on what to expect from delivery
• Consider your subsoil. If your existing ground is hard clay, you might benefit from improving it with topsoil rather than just layering fresh topsoil on top
• Depth matters more than area. A thin layer of topsoil over a large area gives worse results than a proper depth over a smaller area. Don't skimp on depth to stretch your budget further — it's a false economy

Quick Reference Table

For most domestic garden projects, 2-4 bulk bags is typical. For a full garden makeover on a new-build, expect 6-12 bulk bags depending on the size of the plot and how deep your topsoil needs to be.