Topsoil Calculator

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^M
• Volume: 2.88 x 0.30 = 0.864 m³^M
• Litres: 0.864 x 1,000 = 864 litres^M
• 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^M
• Volume: 24 x 0.15 = 3.6 m³^M
• Litres: 3,600 litres^M
• 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. For sowing, the RHS says to dig or rotovate hard, compacted soil to about 20cm (8in), then leave it to settle for several days, ideally five to six weeks.¹

Recommended Topsoil Depths

Not sure how deep to fill? These are topsoil depths for common UK garden projects. Rows with a source number follow the RHS; the rest are our own working figures.

The RHS topsoil guide sets minimums for some jobs: at least 10cm (4in) of topsoil for laying lawns, and about 20cm (8in) or more for new beds.² The turf and new bed rows above use those figures. The other rows are working ranges.

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. The RHS makes a similar point for lawns: disturbed ground settles over time and the surface can drop, so leave it a little higher than the lawn next to it.³

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. The RHS says general-purpose topsoil comes in different screen sizes: coarser grades suit turf laying, and finer grades are good for top dressing lawns.² Expect to pay £50–70 per bulk bag delivered.

Premium Grade Topsoil

Independently laboratory-tested for pH, organic matter content, stone percentage and contamination. BS 3882 is the British Standard for topsoil quality.⁴ 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. The RHS says premium grade can be expensive but should not bring in weed seeds.² The current 2015 version of the standard sets requirements for multipurpose topsoil and for specialist topsoils that are low fertility, acidic or calcareous.⁴ Budget £70–100 per bulk bag.

Sandy Loam Topsoil

The ideal soil texture for most plants. Sandy soils drain quickly, are easy to work and warm up faster in spring than clay, and loams are fertile and well drained.⁵ 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.

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. The RHS mix is a little different: seven parts topsoil, three parts organic matter such as garden compost, and two parts sharp sand.⁶

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.

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The crossover point

For anything under 500 litres (20 bags of 25L), individual bags from a garden centre or The Range 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. Check what you plan to grow first. The RHS says 30cm (1ft) is deep enough for dwarf bulbs, salad leaves and strawberries, but most plants, especially fruit bushes, shrubs and small trees, need 45cm (18in) or more.⁶

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. For beds deeper than 50cm (20in), the RHS suggests filling the base with rubble or subsoil, which helps drainage and cuts the amount of good soil you need.⁶

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.

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). For what it costs per square metre at each depth, see our topsoil cost per m² guide. For the same conversion across gravel, sand and bark, see how many litres in a tonne. 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.

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. When you fill, the RHS says to stop around 5cm (2in) below the rim, firm the soil and leave it to settle for a couple of weeks, topping up if needed.⁶

Frequently Asked Questions

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.

Affiliate links: GardenCalc may earn a commission if you buy through the partner links on this page, at no extra cost to you.

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.²
• 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.²
• 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.²
• Tested to BS 3882. BS 3882 is the British Standard for topsoil traded in the UK, and the current 2015 edition specifies multipurpose topsoil rather than any economy or premium grade.⁴ Reputable suppliers lab-test for pH, organic matter, stone content and contamination, and should be able to show a certificate. The RHS guide quotes pH 5.5 to 7.8 for premium grade and 5.0 to 8.2 for general-purpose and economy grades, taken from the 2007 version of the standard.²
• 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.⁷

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 6.5–7.⁸ That is the "ready to plant" spec the checklist above is asking for, and their own product notes are honest about the limits — they cannot guarantee their topsoil is completely free of weed seeds.⁹

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 and checking notes

Checked by Gary Hodson on 8 October 2026. The RHS pages cover grades, soil prep and the recommended depths. The turf, new bed and raised bed rows of the depth table now use the RHS figures; the other rows do not. BSI covers the standard and GOV.UK the peat news. The seller pages only back the details of the two blended topsoils named above.

1. Royal Horticultural Society — How to Sow a Lawn From Seed. rhs.org.uk/lawns/lawns-from-seed. Checked 16 September 2026: “If the soil is hard and compacted, dig or rotovate to a depth of about 20cm (8in)”; “After digging, leave for several days to settle – the longer the better, ideally five to six weeks”.
2. Royal Horticultural Society — Topsoil: Buying Guide. rhs.org.uk/soil-composts-mulches/topsoil-buying. Checked 16 September 2026: “For laying lawns you will need at least 10cm (4in) layer of top soil”; “New beds will need about 20cm (8in) or more”; “Coarser grades are particularly useful for turf laying while finer grades are good for top dressing lawns”; “Premium grade: This can be expensive but should not bring in weed seeds”; “Look out for high stone content, thick fibrous roots, weeds and contaminants such as glass and brick”; “Ask the supplier where it is coming from”; “imported topsoil can sometimes introduce invasive plants, such as Japanese knotweed and couch grass”. Its BS3882:2007 table gives premium grade pH 5.5-7.8, and general purpose and economy grade pH 5.0-8.2. It does not give a figure for settlement.
3. Royal Horticultural Society — How to Lay Turf. rhs.org.uk/lawns/lawns-from-turf. Checked 16 September 2026: “If your new area of lawn is on disturbed soil, such as an old flower bed, bear in mind that the ground will settle over time and the surface level may drop a little.” It gives no settlement percentage, so the 10–15% allowance is not taken from it.
4. BSI — BS 3882:2015 Specification for topsoil. knowledge.bsigroup.com/products/specification-for-topsoil. Checked 16 September 2026: “BS 3882 on the specification for topsoil covers natural and manufactured topsoils that are moved or traded, not topsoils remaining in situ. It specifies requirements both for multipurpose topsoil, fit for the majority of needs, and for specialist topsoils that have low fertility or are acidic or calcareous.” Used for the standard’s title and scope only.
5. Royal Horticultural Society — Soil types. rhs.org.uk/soil-composts-mulches/soil-types. Checked 16 September 2026: “these soils drain quickly after rain or watering, are easy to cultivate and work. They warm up more quickly in spring than clay soils” (sandy soils); “Loams are comprised of a mixture of clay, sand and silt that avoid the extremes of clay or sandy soils and are fertile, well-drained and easily worked”.
6. Royal Horticultural Society — How to make a raised bed. rhs.org.uk/garden-features/how-to-make-a-raised-bed. Checked 8 October 2026: “Depth - 30cm (1ft) is deep enough for dwarf bulbs, salad leaves and strawberries, but most plants, especially fruit bushes, shrubs and small trees, need 45cm (18in) or more.”; “three parts organic matter (such as garden compost, leafmould or well-rotted manure), two parts sharp sand and seven parts topsoil is sufficient for most raised beds”; “For beds deeper than 50cm (20in), remove any turf and the underlying topsoil, replacing with rubble or subsoil to ensure good drainage and reduce the quantity of good soil needed to fill the bed”; “Fill the bed to around 5cm (2in) below the rim. Firm down the soil and leave it to settle for a couple of weeks, topping the level up again if necessary.”
7. GOV.UK / Defra — Sale of horticultural peat to be banned in move to protect England’s precious peatlands (27 August 2022). gov.uk/government/news/sale-of-horticultural-peat-to-be-banned. Checked 16 September 2026: “All sales of peat to amateur gardeners in England will be banned by 2024, the Government has announced today”; “The RHS stopped selling peat-based growing media bags in 2019”. This is the 2022 announcement; it does not say whether the ban has since come into force.
8. Gardening Naturally — Organic Blended Topsoil product information. gardening-naturally.com/collections/soil/products/organic-blended-topsoil. Checked 16 September 2026: “pH 6.5-7”; “10mm Screened”; “The organic compost has been PAS100 certified.” This is the seller’s own product page, not an independent source.
9. Gardening Naturally — Fruit & Veg Topsoil product information. gardening-naturally.com/collections/soil/products/fruit-vegetable-topsoil-organic-compost. Checked 16 September 2026: “We can’t guarantee 100% against weed seeds in your topsoil as it is not chemically treated”. This is the seller’s own product page, not an independent source.
10. National Institute of Standards and Technology (NIST) — SI Units – Volume. nist.gov/pml/owm/si-units-volume. Checked 21 September 2026: “Liter (L) is a special name for the cubic decimeter (dm 3 )”; “1000 L = 1 m 3”. Used only for the litres-to-cubic-metres conversion.

M — GardenCalc’s own arithmetic, not an external source. Area = length × width; volume = area × depth in metres; litres = cubic metres × 1,000. One square metre at 10cm deep is 0.1 cubic metres, which is 100 litres. The method is fixed; only your measurements change.

Left uncited on purpose: bag and bulk bag prices, tipper prices and the savings worked from them are GardenCalc estimates, not quotes from a named source. The 1.2 tonnes per cubic metre weight, the 850 litre bulk bag, the 800 to 1,000 kg bag weight and the wet-soil figures are working figures, and 1.2 tonnes is the density the calculator uses, so they stay as they are until a technical source is checked. All the other depth table rows (root vegetables, new lawn from seed, top-dressing, lawn levelling and tree planting pits), the 10–15% settlement allowance, the 60/40 mix, the 90cm bag and 75cm gate sizes and the “underestimate by at least 30%” line have no source on this page. In the FAQ, only the turf and new bed depths (source 2), the raised bed depths (source 6) and the litres-per-cubic-metre conversion (source 10) have been checked; every other figure in those answers, and the rest of the FAQ, has not been checked yet. The 10 to 20mm screen size is also uncited.

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