Calculate Your Topsoil
Choose your area shape, enter dimensions and topsoil depth. We calculate volume, bag counts, bulk bags, weight and estimated cost.
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How Much Topsoil Do I Need?
The formula is simple: Length (m) x Width (m) x Depth (m) = Volume (m³). Multiply by 1,000 to convert to litres. The tricky part is knowing the right depth for your project, which is why we built this topsoil calculator with recommended depths built in.
A small raised bed needs surprisingly large volumes. A standard 2.4m x 1.2m bed at 30cm deep requires 864 litres -- that is 35 bags of 25-litre topsoil or two bulk bags. Most people underestimate by at least 30%, which means a second delivery charge and a frustrating delay mid-project.
This calculator handles rectangles, circles and L-shaped areas. It gives you results in cubic metres, litres, 25L bags, 40L bags, bulk bags (850 litres) and approximate weight in tonnes. It also estimates cost at 2026 UK prices so you can budget before ordering.
Worked Example: Raised Bed
A 2.4m x 1.2m raised bed filled to 30cm deep:
- Area: 2.4 x 1.2 = 2.88 m²
- Volume: 2.88 x 0.30 = 0.864 m³
- Litres: 0.864 x 1,000 = 864 litres
- 25L bags: 864 ÷ 25 = 35 bags (at £5 each = £175)
- Bulk bags: 2 bulk bags (at £65 delivered = £130)
Two bulk bags (£130) still save £45 versus £175 in individual bags. For multiple beds, the savings compound rapidly.
Worked Example: New Lawn
A 6m x 4m lawn area prepared to 15cm depth for grass seed:
- Area: 6 x 4 = 24 m²
- Volume: 24 x 0.15 = 3.6 m³
- Litres: 3,600 litres
- Bulk bags: 3,600 ÷ 850 = 5 bulk bags
- Weight: 3.6 x 1.2 = 4.3 tonnes
At this volume, ask your supplier about a loose tipper delivery -- it is typically £35-50 per cubic metre versus £65-80 per bulk bag. Once the topsoil is down, use our grass seed calculator to work out the right seeding rate.
Recommended Topsoil Depths
Not sure how deep to fill? These are the recommended topsoil depths for the most common UK garden projects, based on horticultural best practice.
| Project | Depth (cm) | Depth (inches) | Notes |
|---|---|---|---|
| Raised bed (vegetables) | 25–30 | 10–12 | Deep enough for most crops including tomatoes and beans |
| Raised bed (root veg) | 30–45 | 12–18 | Carrots, parsnips and potatoes need the full depth |
| Flower border | 15–20 | 6–8 | Sufficient for bedding plants and most perennials |
| New lawn (seed) | 10–15 | 4–6 | 15cm gives much better drought resistance than 10cm |
| New lawn (turf) | 5–10 | 2–4 | Turf brings its own root zone -- less topsoil needed |
| Lawn top-dressing | 1–2 | ½–1 | Thin layers only -- thicker smothers the grass |
| Lawn levelling | 2–5 | 1–2 | Use fine screened topsoil to fill hollows |
| Tree planting pit | 45–60 | 18–24 | Backfill with a 75/25 mix of topsoil and compost |
Settlement allowance: Fresh topsoil settles by 10–15% in the first few weeks. If you need a finished depth of 30cm, fill to 33–35cm initially. The calculator gives you the volume for your target depth -- add 10–15% on top to account for this.
Topsoil Types for Different Projects
Not all topsoil is the same. The type you buy should match your project. Here are the main types available in the UK and where each one works best.
General Purpose Screened Topsoil
Natural soil passed through a 10–20mm mesh to remove stones, roots and debris. This is the standard option for most garden projects -- borders, raised beds, lawn preparation and general landscaping. Quality varies between suppliers, so always ask whether it has been screened and what the source is. Expect to pay £50–70 per bulk bag delivered.
Premium BS 3882 Topsoil
Independently laboratory-tested for pH, organic matter content, stone percentage and contamination. BS 3882 is the British Standard for topsoil quality, and any reputable bulk supplier should be able to show you the certificate. Premium grade is the best choice for vegetable beds and new lawns where soil quality directly affects results. Budget £70–100 per bulk bag.
Sandy Loam Topsoil
The ideal soil texture for most plants. Sandy loam drains freely, warms up quickly in spring, and is easy to work even after rain. If your garden sits on heavy clay, importing sandy loam for raised beds transforms growing conditions. Particularly good for root vegetables, herbs and Mediterranean plants. Typically £80–110 per bulk bag.
Blended Raised Bed Topsoil
Pre-mixed topsoil and compost (usually 60/40 or 70/30 blend) sold specifically for filling raised beds. The advantage is convenience -- you fill and plant without mixing. The downside is cost: £90–120 per bulk bag versus £65–70 for plain topsoil plus £30–40 for a bag of compost to mix yourself. For small projects it saves time; for larger orders, mixing your own is significantly cheaper.
| Topsoil Type | Price per Bulk Bag | Best Use |
|---|---|---|
| General Purpose (screened) | £50–70 | Borders, lawns, general landscaping |
| Premium BS 3882 | £70–100 | Vegetable beds, fine lawns |
| Sandy Loam | £80–110 | Clay gardens, root veg, drainage |
| Blended Raised Bed | £90–120 | Raised beds (ready to plant) |
| Unscreened (budget) | £30–50 | Backfilling, raising ground levels |
Planning to mix your own raised bed soil? Use the calculator above for the total volume, then split your order: 60% topsoil and 40% compost. Mix them as you fill the bed. This is cheaper and gives you control over quality.
Bags vs Bulk Bags -- When to Order in Bulk
The way you buy topsoil affects the final cost more than the type of soil you choose. Here is a straightforward price comparison for 2026 so you can pick the right option.
| How You Buy | Volume | Typical Price | Cost per m³ |
|---|---|---|---|
| 25L bags (garden centre) | 25 litres | £4–7 per bag | £160–280 |
| 40L bags (garden centre) | 40 litres | £5–8 per bag | £125–200 |
| Bulk bag (delivered) | 850 litres | £50–100 delivered | £60–120 |
| Loose tipper load | 3+ m³ | £35–50 per m³ | £35–50 |
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The crossover point
For anything under 500 litres (20 bags of 25L), individual bags from a garden centre or Amazon are the simplest option. Between 500 and 2,500 litres, bulk bags are the sweet spot -- cheaper per litre than bags and most suppliers deliver for a flat fee. Above 3 cubic metres (3,000 litres), ask about loose tipper delivery. It is the cheapest per-tonne option but requires vehicular access and a place to dump the heap.
Delivery considerations
Bulk bags weigh close to a tonne. The delivery driver uses a crane or forklift to place the bag, so you need a firm surface within reach of the lorry -- a driveway or paved area works well. Soft lawn does not: the weight will leave a deep depression. If your only access is through a side gate, measure the width first. Most bulk bags are 90cm x 90cm and will not fit through a standard 75cm gate. In that case, individual bags carried by hand may be the only practical option despite the higher cost.
How Many Bags of Topsoil for a Raised Bed?
Raised beds are the single most common reason people use this topsoil calculator. Here are the exact quantities for popular UK raised bed sizes, calculated at a standard 30cm fill depth.
| Raised Bed Size | Volume Needed | 25L Bags | 40L Bags | Bulk Bags |
|---|---|---|---|---|
| 1.2m x 0.6m (4ft x 2ft) | 216 litres | 9 | 6 | — |
| 1.2m x 1.2m (4ft x 4ft) | 432 litres | 18 | 11 | 1 |
| 1.8m x 0.9m (6ft x 3ft) | 486 litres | 20 | 13 | 1 |
| 2.4m x 1.2m (8ft x 4ft) | 864 litres | 35 | 22 | 2 |
| 3.0m x 1.2m (10ft x 4ft) | 1,080 litres | 44 | 27 | 2 |
| 3.6m x 1.2m (12ft x 4ft) | 1,296 litres | 52 | 33 | 2 |
Money-saving tip: For any bed needing more than 500 litres, a bulk bag at £65 delivered is dramatically cheaper than individual bags. A 2.4m x 1.2m bed filled with 25L bags costs roughly £175; the same volume in two bulk bags costs £130. That is a £45 saving on one bed alone.
Want the exact soil mix breakdown including compost and drainage material? Use our dedicated raised bed soil calculator which handles L-shaped layouts and shows the 60/30/10 mix split.
Topsoil Coverage Calculator -- Litres Per Square Metre
A quick-reference table showing how much topsoil covers one square metre at different depths. Useful for estimating before you measure.
| Depth | Litres per m² | Tonnes per m² | Typical Use |
|---|---|---|---|
| 2cm | 20 litres | 0.024 t | Lawn top-dressing |
| 5cm | 50 litres | 0.06 t | Lawn levelling, bed refresh |
| 10cm | 100 litres | 0.12 t | Shallow borders, turf prep |
| 15cm | 150 litres | 0.18 t | New lawns, flower beds |
| 20cm | 200 litres | 0.24 t | Deep borders, shrub planting |
| 30cm | 300 litres | 0.36 t | Raised beds, vegetable growing |
| 45cm | 450 litres | 0.54 t | Deep raised beds, root crops |
Weight conversion: Topsoil weighs approximately 1.2 tonnes per cubic metre when loose and dry. One tonne of topsoil is roughly 830 litres (0.83 m³). Wet topsoil after rain is significantly heavier -- up to 1.5 tonnes per cubic metre.
How Much Does a Bulk Bag of Topsoil Cover?
A standard bulk bag holds approximately 850 litres (0.85 m³) and weighs 800–1,000 kg. Here is how far one bulk bag stretches at different depths.
| Depth | Area Covered by 1 Bulk Bag | Typical Project |
|---|---|---|
| 5cm | 17 m² | Top-dressing a small lawn |
| 10cm | 8.5 m² | Shallow border or turf preparation |
| 15cm | 5.7 m² | New lawn from seed |
| 20cm | 4.3 m² | Flower border |
| 30cm | 2.8 m² | Most of a 2.4m x 1.2m bed (needs 2) |
As you can see, a bulk bag does not go as far as most people expect -- especially at raised bed depths. A single 2.4m x 1.2m bed needs just over one bulk bag -- round up to two. If you are filling multiple beds, order accordingly and always round up.
Frequently Asked Questions
How much topsoil do I need?
Multiply your area (length x width in metres) by the depth (in metres) to get the volume in cubic metres. Multiply by 1,000 to convert to litres. For example, a 3m x 2m area at 15cm deep needs 3 x 2 x 0.15 = 0.9 m³ (900 litres). That is roughly 2 bulk bags or 36 bags of 25-litre topsoil. Use the calculator at the top of this page for an instant answer.
How many bags of topsoil for a raised bed?
For a standard 2.4m x 1.2m raised bed at 30cm deep: 864 litres = 35 bags of 25L or 22 bags of 40L or 2 bulk bags. For a smaller 1.2m x 1.2m bed: 432 litres = 18 bags of 25L. Always fill to at least 30cm for vegetables as soil settles 10–15% in the first few weeks. See the raised bed table above for more sizes.
How deep should topsoil be?
Raised beds for vegetables: 25–30cm. Flower borders: 15–20cm. New lawn from seed: 10–15cm. Laying turf: 5–10cm. Lawn top-dressing: 1–2cm. Root vegetables (carrots, parsnips): 30–45cm. Tree planting pits: 45–60cm. See the full depth guide table above for detailed recommendations.
How much does a bulk bag of topsoil weigh?
A standard bulk bag weighs 800–1,000 kg (roughly 1 tonne), holding approximately 850 litres (0.85 m³). Moisture content significantly affects weight -- a bag left in the rain can exceed 1.1 tonnes. Always place bulk bags on a hard surface like a driveway. Soft lawn will be badly damaged by the weight.
What is the difference between topsoil and compost?
Topsoil is natural earth from the upper 150–200mm of the ground, screened to remove stones. It provides structure, bulk and drainage. Compost is decomposed organic matter -- rich in nutrients and beneficial microbes but lighter. For raised beds, mix 60% topsoil with 40% compost for the ideal balance. For refreshing existing borders, a 5–10cm layer of pure compost forked in works best.
How many bags of topsoil do I need?
At 15cm depth, one square metre needs 150 litres = 6 bags of 25L topsoil. A 10 m² area at 15cm deep needs 1,500 litres = 60 bags of 25L or 2 bulk bags. At 30cm depth, double those figures. Enter your exact dimensions into the calculator above for a precise count.
How much topsoil do I need per square metre?
It depends on depth. At 10cm: 100 litres per m². At 15cm: 150 litres per m². At 30cm: 300 litres per m². For lawn top-dressing at 2cm: just 20 litres per m². See the full coverage table above for all depths.
Is it cheaper to buy topsoil in bags or bulk?
Bulk is always cheaper per litre. Individual 25L bags cost £4–7 each (£160–280 per m³). A bulk bag holding 850 litres costs £50–100 delivered (£60–120 per m³). For anything over 500 litres, bulk bags save money. For over 3,000 litres, a loose tipper delivery at £35–50 per m³ is the best value.
What is BS 3882 topsoil?
BS 3882 is the British Standard for topsoil quality. It classifies topsoil into three grades -- Economy, Multipurpose and Premium -- based on independent laboratory testing for pH, organic matter, stone content, particle size and contamination. Premium grade BS 3882 has a pH between 5.5 and 7.5 and guaranteed minimum organic matter content. Always ask for the certificate when ordering in bulk.
When is the best time to buy topsoil?
Spring (March–May) and autumn (September–October) are ideal. In spring, the ground is workable and you can plant immediately. In autumn, winter rain and frost help new topsoil settle before the growing season. Avoid mid-winter when frozen ground makes spreading impossible, and summer when dry topsoil is dusty and difficult to level.
How many litres is 1 tonne of topsoil?
One tonne of topsoil is approximately 830 litres (0.83 cubic metres) when loose and dry. Moisture content makes a big difference — wet topsoil is denser, so 1 tonne of damp topsoil may only be 650–750 litres. For ordering purposes, assume 1 tonne = 1 bulk bag (850 litres). To convert the other way, 1,000 litres of dry topsoil weighs roughly 1.2 tonnes.
How do I prepare my soil before adding topsoil?
Remove weeds, large stones and debris from the existing surface. Fork over compacted ground to a depth of 15–20cm so the new topsoil bonds with the layer beneath — skipping this creates a drainage barrier. If the existing soil is heavy clay, work in horticultural grit before adding topsoil. Spread topsoil in layers of 10–15cm at a time, lightly firming each layer. Water gently and allow to settle for 7–14 days before planting.
How many 20kg bags of topsoil are in 1 cubic metre?
Approximately 60 bags. Dry topsoil weighs about 1,200kg per cubic metre, so 1,200 ÷ 20 = 60 bags. In practice, buy 65 bags to allow for waste and settling. Note that 20kg bags are sold by weight, not volume — each 20kg bag holds roughly 16–17 litres of topsoil depending on moisture content.
What is the difference between topsoil and garden soil?
Topsoil is raw, screened earth from the upper layer of the ground — it provides bulk and structure but limited nutrients. Garden soil (sometimes called planting soil) is topsoil blended with compost, fertiliser and sometimes perlite or bark to create a ready-to-plant mix. Topsoil is cheaper and better for filling large areas. Garden soil is more expensive but saves mixing — ideal for smaller beds and containers.
How many 25kg bags make a cubic metre?
Approximately 48 bags. Dry topsoil weighs about 1,200kg per cubic metre, so 1,200 ÷ 25 = 48 bags. For 25-litre bags (sold by volume, not weight), you need 40 bags per cubic metre since 1 cubic metre = 1,000 litres. Always check whether the bag is labelled in kg or litres — it changes the number you need significantly.
Best Topsoil Products UK 2026
Whether you are filling raised beds or preparing a new lawn, these are popular topsoil products you can buy in the UK right now.
| Product | Size | Best For | Buy |
|---|---|---|---|
| Westland Multi-Purpose with John Innes | 60L | Raised beds -- a popular multipurpose mix | Coco & Coir |
| Rolawn Blended Loam Topsoil | Bulk bag (1m³) | Best bulk topsoil -- screened, weed-free, BS 3882 | Amazon |
| Miracle-Gro Raised Bed Soil | 42L | Pre-mixed raised bed soil -- fill and plant | Amazon |
| Horticultural Grit (Coarse) | 25kg | Drainage improvement for clay soils and herb beds | Amazon |
| Soil pH Test Kit | Kit | Test before planting -- avoid pH problems | Amazon |
| Coco & Coir Rose, Tree & Shrub Compost | 40L | Peat-free planting compost -- blends with topsoil | Coco & Coir |
Links above are affiliate links -- as an Amazon Associate we earn from qualifying purchases.
Choosing Topsoil: A Buyer's Checklist
At the budget end, topsoil is sold loose and largely unregulated, so quality varies a lot from one supplier to the next. Before you order — especially a tonne-plus bulk bag that is awkward to send back — here is what actually matters.
- Screened and clean. Good topsoil is sieved to take out stones, thick roots and debris. The RHS says to watch for high stone content, fibrous roots, weeds and bits of glass or brick — all tell-tales of cheap, as-dug fill.1
- Known origin. Soil stripped from building sites can be wildly variable. The RHS advice is to ask the supplier where the soil came from and to request a soil analysis in writing.1
- No hitchhikers. Imported topsoil is a common route for invasive weeds such as Japanese knotweed and couch grass to reach a garden, so a reputable supplier should be able to explain how theirs is sourced.1
- BS 3882 graded. BS 3882 is the British Standard for topsoil traded in the UK.2 Reputable suppliers lab-test for pH, organic matter, stone content and contamination, and should be able to show a certificate. For beds and borders, look for a graded topsoil with a pH in the roughly 5.5–7.5 range.1
- Peat-free. The RHS stopped selling peat-based compost in 2019, and the government has announced plans to end bagged peat sales to home gardeners in England. A peat-free blended topsoil does the same job without draining a carbon-rich habitat.3
A peat-free pick for bulk fills
For filling raised beds and new borders, we point gardeners towards Gardening Naturally's peat-free blended topsoils rather than as-dug soil of unknown origin. They are 10mm screened, blended with PAS 100 compost and pH-balanced around 6.5–7.4 That is the "ready to plant" spec the checklist above is asking for, and their own product notes are honest about the limits — no topsoil can be guaranteed completely free of weed seeds.5
Affiliate links — we earn a small commission at no extra cost, and only point to products that match the advice above.
Whatever you order, buy a little extra — fresh topsoil settles as it beds in over the first couple of weeks, so it is worth keeping a bag spare.
Sources
- Royal Horticultural Society — Topsoil: buying (accessed 27 June 2026).
- BS 3882:2015 topsoil specification — NRM-Cawood technical summary (accessed 27 June 2026).
- GOV.UK / Defra — Sale of horticultural peat to be banned (27 August 2022).
- Gardening Naturally — Organic Blended Topsoil product information (accessed 27 June 2026).
- Gardening Naturally — Fruit & Veg Topsoil product information (accessed 27 June 2026).
Related Calculators
Planning a bigger project? These calculators work alongside the topsoil calculator to help you get every quantity right.
- Compost Calculator -- Work out how much compost to mix with your topsoil
- Raised Bed Calculator -- Soil mix breakdown for raised beds including L-shapes
- Grass Seed Calculator -- Seeding rates for new lawns over fresh topsoil
- Mulch Calculator -- Bark mulch quantities for weed suppression after planting
- Turf Calculator -- How many turf rolls for your new lawn
- Fertiliser Calculator -- Feed your new topsoil at the right application rate