How Much Topsoil Do I Need?
Whether you are laying a new lawn, filling raised beds, levelling a garden or improving your borders, getting the right amount of topsoil is essential. Order too little and you will have to make a second delivery — often at a higher price. Order too much and you have expensive material left over with nowhere to put it.
This guide shows you exactly how to calculate how much topsoil you need — in cubic metres, tonnes and bags — for any garden project.
How to Calculate How Much Topsoil You Need
The calculation is straightforward. You need three measurements:
- Area — the length × width of the area you are filling in metres
- Depth — how deep you want the topsoil layer in metres
- Wastage — add 10% to allow for settlement and uneven spreading
Volume (m³) = Length (m) × Width (m) × Depth (m)
Then add 10% for wastage and settlement:
Order quantity = Volume × 1.10
Worked Example — New Lawn
You want to lay a new lawn on an area 10 metres long and 8 metres wide. You want 100mm (0.1m) of topsoil as a growing medium before laying turf.
Area = 10 × 8 = 80m²
Volume = 80 × 0.1 = 8.0m³
With 10% wastage = 8.0 × 1.10 = 8.8m³ to order
How Deep Should Topsoil Be?
The depth of topsoil you need depends on what you are using it for:
| Application | Recommended Depth |
|---|---|
| New lawn — turf or seed | 100mm (4 inches) |
| Flower beds and borders | 200-300mm (8-12 inches) |
| Raised beds — vegetables | 300-400mm (12-16 inches) |
| Tree planting | 400-600mm (16-24 inches) |
| Top dressing existing lawn | 10-25mm (½-1 inch) |
| Levelling uneven garden | Varies — measure deepest point |
How to Convert m³ to Tonnes
Topsoil is often sold and delivered by the tonne. To convert your volume in m³ to tonnes multiply by the density of topsoil:
Premium topsoil density = approximately 1.0 tonne per m³
So for our example:
8.8m³ × 1.0 = 8.8 tonnes
Note that topsoil density varies depending on its composition and moisture content. Sandy topsoil is lighter (around 0.9t/m³) and clay-rich topsoil is heavier (around 1.2t/m³). When in doubt use 1.0t/m³ as a good general estimate.
How Many Bags of Topsoil Do I Need?
If you are buying bagged topsoil from a garden centre rather than ordering in bulk, here is how to work out how many bags you need:
| Bag Size | Volume per Bag | Bags per m³ |
|---|---|---|
| 20 litre bag | 0.020m³ | 50 bags |
| 40 litre bag | 0.040m³ | 25 bags |
| 50 litre bag | 0.050m³ | 20 bags |
| Jumbo bag (0.75m³) | 0.750m³ | 1.3 bags |
| Bulk tipper (15 tonne) | 15.0m³ | 1 load |
For our example of 8.8m³ using 40 litre bags:
8.8 ÷ 0.040 = 220 bags
That is a lot of bags — for anything over 2m³ it is much more cost effective to order bulk topsoil by the tonne from a landscape supplier or builder’s merchant.
Quick Reference — Topsoil Quantities for Common Projects
| Project | Area | Depth | Volume | Tonnes (approx) |
|---|---|---|---|---|
| Small lawn 5m × 4m | 20m² | 100mm | 2.2m³ | 2.2t |
| Medium lawn 10m × 8m | 80m² | 100mm | 8.8m³ | 8.8t |
| Large lawn 15m × 12m | 180m² | 100mm | 19.8m³ | 19.8t |
| Flower border 10m × 1m | 10m² | 200mm | 2.2m³ | 2.2t |
| Raised bed 3m × 1.2m | 3.6m² | 400mm | 1.6m³ | 1.6t |
| Veg patch 5m × 3m | 15m² | 300mm | 4.95m³ | 4.95t |
All quantities include 10% wastage allowance.
What Type of Topsoil Should I Order?
Not all topsoil is the same. There are several grades available in the UK:
- Economy topsoil — screened soil, suitable for general fill and levelling. Not ideal for planting.
- General purpose topsoil — screened and blended, suitable for most garden applications including lawns and borders.
- Premium topsoil — BS 3882 certified, tested for pH, nutrients and organic matter. Best for new lawns, vegetable gardens and planting beds.
- Turf dressing — fine screened, used for top dressing existing lawns and levelling.
- Enriched topsoil / planting compost mix — topsoil blended with compost, ideal for raised beds and borders.
For new lawns and planting always use BS 3882 certified topsoil — it guarantees a minimum standard of quality and nutrient content.
Tips for Ordering Topsoil
- Always add 10% wastage — topsoil settles after laying and you lose material at the edges. Never order the exact calculated amount.
- Check access for delivery — a bulk tipper lorry needs good access and a suitable drop-off point. Jumbo bags can be placed more precisely but cost more per tonne.
- Order all in one delivery — topsoil can vary in colour and composition between batches. Order everything you need at once.
- Check the pH — for lawns and most plants you want a pH of 6.0-7.0. Ask your supplier for the pH of the topsoil before ordering.
- Avoid ordering when wet — wet topsoil is significantly heavier than dry topsoil. If you are ordering by weight you may get less volume than expected after a wet period.
How LandscapeBOQ Calculates Topsoil Quantities Automatically
If you are a landscape contractor quoting jobs that include topsoil supply, doing these calculations manually for every job takes time. LandscapeBOQ has a dedicated Topsoil & Mulch calculator that does everything automatically.
Enter your area, depth, material type and delivery method — and it calculates instantly:
- Volume in m³
- Weight in tonnes
- Number of deliveries or bags required
- Total material and delivery costs using your own unit rates
The topsoil calculator feeds directly into the BOQ Master alongside turf, paving, fencing and all other elements of the job — generating a complete priced Bill of Quantities in one click.
Try LandscapeBOQ free for 7 days — no card required →
Summary — How Much Topsoil Do I Need?
- Measure your area — length × width in metres
- Decide on your depth — 100mm for lawns, 200-400mm for beds and borders
- Calculate volume — area × depth in metres
- Add 10% wastage — multiply by 1.10
- Convert to tonnes — multiply m³ by 1.0 for standard topsoil
- Choose your delivery method — bulk tipper for large quantities, jumbo bags for restricted access, small bags only for very small areas
Getting your topsoil quantity right saves money, avoids delays and ensures your lawn, beds and borders get the depth of growing medium they need to thrive.