Free UK construction calculators Metric and imperial 2026 UK prices
Work out how much topsoil you need for lawns, borders, planting beds and raised planters. Measure your space, choose a soil depth and calculate cubic metres, cubic yards, litres, approximate tonnes, bag quantities and an optional delivery budget before you order.
Estimated Topsoil To Order
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| Bag Size | Usable Volume | Bags Needed |
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Bag counts round up. Verify the actual volume sold per bag and delivery weight; labels such as “tonne bag” are not a fixed litre measurement.
| Margin | Soil Volume | Selected Bags |
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All scenarios keep your settlement allowance and selected bag size unchanged. The selected margin is highlighted.
The Topsoil Calculator helps turn a garden measurement into a quantity you can confidently discuss with a soil supplier. It handles a rectangular lawn, a circular feature, a raised planter, an already-known area, an already-known volume and a bag count. Each method converts the input to cubic metres first, so the same ordering comparison can then show bulk quantities and bag options.
If you are preparing several beds, it is often better to calculate each bed separately. A small flower border may need a deeper layer than a lawn even when their square metre areas are similar. Re-using one depth for both areas can produce an inaccurate combined order.
Every topsoil order starts with geometric volume. For a rectangular area, multiply the surface length and width by the required layer thickness. Convert millimetres into metres first. The resulting cubic metres describe the volume of topsoil needed to cover the measured area at the specified depth.
A cubic metre is 1,000 litres, approximately 1.308 cubic yards or 35.315 cubic feet. The calculation keeps sufficient precision during the maths and rounds only the displayed values and whole bag counts. For a raised bed, the rectangular formula uses the inside measurements, multiplied by the number of identical planters.
Important distinction: volume and weight are different quantities. A layer occupying 2 m³ might weigh much more or less than two tonnes, depending on the soil composition, moisture and bulk density. This calculator does not assume that one cubic metre equals one tonne.
A rectangular lawn measures 8 m long and 5 m wide. Its surface area is 40 m². At 100 mm (0.10 m) depth, the measured topsoil volume is 4.00 m³. Applying a 10% ordering margin and no extra settlement gives 4.40 m³ to order. If you select 1,000-litre bags with their full nominal volume confirmed, you would need five bags, whereas a supplier delivering loose material might quote directly for 4.4 cubic metres.
A round planting bed has a diameter of 3 m and needs 200 mm of topsoil. Its area is approximately 7.069 m². Multiplying by 0.2 m gives about 1.414 m³. With a 10% margin, the order estimate becomes roughly 1.56 m³. That is around 39 bags of 40 litres when whole bags are rounded up.
Two identical planters each have internal dimensions of 2.4 m by 1.2 m, with a desired topsoil fill of 350 mm. Together they require 2 × 2.4 × 1.2 × 0.35 = 2.016 m³ before allowances. A 10% margin lifts the quantity to approximately 2.22 m³. This assumes all of that space will be filled with topsoil: reduce the measured fill depth if some space is occupied by another approved growing medium.
These examples show why the ordering unit matters. A whole-bag purchase normally rounds upward to the next complete bag, while loose delivery quantities depend on the supplier's minimum increments and actual order sizes.
Topsoil is the upper mineral soil layer used to establish vegetation. It is not simply any soil dug out of the ground. Suitable purchased topsoil should have structure, drainage, texture and fertility appropriate for the intended planting. Existing garden soil may be perfectly useful after preparation, so importing large quantities should not be automatic.
A level, stone-free growing surface is helpful before turf or seed is laid. Calculate the new soil actually being added; deep soil preparation below it is not necessarily a new topsoil order.
Vegetable plots, flower beds and shrub borders often use different soil depths and qualities. Measure separate zones instead of applying one uniform layer to an entire garden.
Use internal dimensions and account for any appropriate blend of topsoil and organic matter. A tall box does not always need to be filled entirely with purchased pure topsoil.
Small dips, reinstated trenches and damaged lawn sections can consume more soil than their visible area suggests. Depth should be checked at several points.
The correct growing medium depends on use. Pure compost is not equivalent to topsoil, and fine top-dressing mixes are not interchangeable with the deeper, general-purpose soil used to make a new lawn.
A topsoil depth is not a universal specification. For new lawns, the Royal Horticultural Society's topsoil buying guidance advises at least around 10 cm, while new planting beds may need 20 cm or more. The required total rooting depth may be much deeper than the imported topsoil layer because plants also use suitably prepared subsoil.
| Garden Use | Illustrative Added Layer | Volume For 10 m² | What To Check |
|---|---|---|---|
| New lawn surface | 100 mm | 1.00 m³ | Existing soil structure and drainage |
| Deeper lawn preparation | 150 mm | 1.50 m³ | Whether depth is added soil or cultivated existing soil |
| New flower bed | 200 mm | 2.00 m³ | Plant requirements and soil below |
| Vegetable bed | 300 mm | 3.00 m³ | Growing mix, fertility and drainage |
| Raised planter fill | 400 mm | 4.00 m³ | Internal fill depth and mix ratio |
These are volume illustrations, not minimum construction standards. Some sites need less imported material because they already have serviceable topsoil. Others need specialist drainage, grading, soil treatment or professional landscape design.
Some UK suppliers sell topsoil by cubic metre, others by tonne or a stated bag capacity. A weight estimate therefore helps when comparing quotes, checking delivery vehicle access or planning manual handling. The calculator provides editable assumptions for loose bulk density, in tonnes per cubic metre, rather than claiming a fixed conversion for every product.
| Topsoil Type | Calculator Assumption | Tonnes For 2 m³ | Reason It May Vary |
|---|---|---|---|
| Screened topsoil | 1.30 t/m³ | 2.60 t | Moisture and the proportion of fine particles |
| Loamy topsoil | 1.35 t/m³ | 2.70 t | Mineral fraction and degree of settling |
| Sandy topsoil | 1.45 t/m³ | 2.90 t | Particle grading and water content |
| Clay-rich topsoil | 1.55 t/m³ | 3.10 t | Wet clay can be much heavier |
| Topsoil/compost blend | 0.95 t/m³ | 1.90 t | Organic matter and moisture content |
| Light prepared soil | 1.15 t/m³ | 2.30 t | Air content and organic additives |
These are illustrative calculation assumptions, not certified product specifications or universal industry values. If a supplier tells you that the selected loose soil weighs 1.22 tonnes per cubic metre, enter 1.22 in the optional density field. The estimate then uses that figure for all calculated tonnage. Do not confuse bulk density with the dry particle density measured in laboratory soil tests.
Buying options are not interchangeable simply because they share a product name. A small 25-litre or 40-litre bag has a labelled volume that is usually straightforward to count. A larger landscaping bag may be marketed as a jumbo or bulk bag, but the actual supply can be 500 L, 600 L, 750 L, 850 L or another declared amount. A “tonne bag” describes an informal name or handling capacity, not a standard cubic-metre quantity.
For example, a requirement of 1.35 m³ is 1,350 litres. That is 34 bags of 40 L, or two 750 L bags. The latter option supplies 1,500 L and leaves some spare. Use the exact capacity your merchant states and verify whether an advertised bag size refers to the soil contents or the outside container dimensions.
Loose tipped delivery may make sense for a large accessible lawn, provided there is a clean, safe unloading area. Bulk bags can be easier to place or store where access is limited. Small bags offer flexibility for smaller jobs but create more packaging and handling work. In all cases, compare delivered cost, not only the product headline price.
The calculator compares bag counts by volume and does not claim that bagged and loose soil have identical moisture, screening, compaction or grade. These differences can affect spreading, final level and the effective cost per cubic metre.
Start with the finished lawn area, excluding paths, patios, sheds and permanent beds. A rectangular lawn is simple to measure; an L-shaped garden can be broken into two rectangles. Multiply each area by the depth of new topsoil you intend to spread, not the total depth of the soil you will cultivate.
Before laying turf, remove weeds and large stones, improve the existing soil where appropriate, correct drainage defects and level the sub-base. The RHS turf-laying guidance discusses preparing the soil and allowing it to settle. Adding a thick topsoil layer over a waterlogged or heavily compacted base is not a reliable substitute for drainage and soil preparation.
To calculate a lawn with slopes, work from measured horizontal areas and the planned average added depth. If you are cutting a high end and filling a low end, some soil may be reused on site. Count only the net soil that must be imported. A survey is more reliable than a single arithmetic estimate for steep or irregular levels.
A raised bed calculation should use the inner length and width, not the external size of timber sleepers or blocks. The fill depth is also measured inside the planter: subtract any freeboard below the rim and any permanent layers that occupy space. For several identical planters, multiply the per-planter result by the number of units.
For unusually tall planters, confirm the recommended soil profile and drainage approach rather than filling the entire structure with premium topsoil by default. The RHS raised-bed guide describes working with combinations of topsoil and organic matter and allowing the material to settle before planting.
Example: an internal bed 2 m × 1 m × 0.3 m needs 0.6 m³ before any allowance. That is 600 litres, or fifteen 40-litre bags if every bag contains its full nominal volume.
Deep containers, roof terraces and balconies can have structural load limits. Wet soil can weigh substantially more than dry soil. Check design loading and drainage before filling elevated or suspended beds.
The ordering margin covers uncertainty in the geometry: overlooked dips, irregular borders, small losses during handling or a layer that finishes marginally thicker than planned. Settlement is a different issue: soil can decrease in volume as it consolidates after placing and watering. The calculator lets you enter both, but keeps the extra settlement default at zero to avoid a hidden duplicate allowance.
For a flat garden with a carefully measured depth, 0–10% may be enough depending on your installation method. For a rough excavation with several varying depths, it may be safer to measure more carefully before raising the percentage. A larger margin should not replace a survey of major hollows or a plan for the finished levels.
The tool first increases the measured volume by the chosen ordering margin and then applies any separately selected settlement allowance. A 10% margin plus 5% settlement gives a multiplier of 1.10 × 1.05 = 1.155, not 1.15. This matters most for larger deliveries.
When buying a known volume of topsoil that has already been delivered, reducing both allowances to zero is usually the clearer way to describe what is on site. Always distinguish “soil already here” from “soil still needed to finish the job.”
Topsoil prices vary by screening grade, source, testing, moisture, quantity, package size and delivery address. The calculator does not make up a live retail price. Instead, it allows you to enter the actual quoted price per selected bag or an alternative bulk price per cubic metre. The result shows them separately so you can compare like for like.
Enter a price for the currently selected 25 L, 40 L, 50 L, 750 L or 1,000 L bag. The calculation rounds the required number of bags up to a whole bag.
Use the merchant's price per actual cubic metre delivered or collected, then confirm any minimum order and haulage fee separately.
Ask whether the quotation includes VAT, unloading, crane or grab access, small-load surcharges, waiting time, packaging and a delivery slot. A cheaper product may be poor value if it contains debris, has the wrong texture or needs extensive remedial work.
Healthy plant establishment depends on more than the headline volume. Ask for the intended use and relevant description of the product: general-purpose landscaping, a screened lawn preparation mix, a more fertile planting blend or a particular specification for a commercial project. Examine for foreign matter, large stones, persistent weeds and inconsistent material before spreading it across a garden.
For specified UK projects, BS 3882:2015 is the referenced British Standard for topsoil. A supplier may provide test information; ask what was tested and whether it describes the batch you will actually receive. Even soil represented as meeting a standard is not automatically confirmed free from every possible human-health risk at a potentially contaminated site. The Leeds City Council guidance highlights the need for site-specific contamination assessment where relevant.
The topsoil calculator measures how much soil would physically fill a space. It cannot assess pH, nutrient balance, invasive weeds, soil-borne disease or suitability for edible crops. Those are separate buying and site-assessment questions.
Plan an unloading location before delivery. A lorry may need clear turning space, suitable ground bearing capacity and an agreed tipping point. A nominally convenient address can still be inaccessible to a large vehicle. Verify the load dimensions and ask the supplier whether lifting, tipping or tail-lift arrangements are included.
Keep soil stockpiles on a clean surface and separate from rubble, subsoil and construction waste. Avoid repeatedly driving heavy machinery over new topsoil. Working very wet soil can compact it and degrade its structure. The topsoil handling guidance from Leeds City Council describes avoiding unsuitable wet conditions, separating soil types and preparing the receiving ground.
Spread the material in a way that preserves structure, grade it carefully to your intended finished level and allow settling where the gardening method requires it. For larger landscaping works, follow the project's design specification rather than adopting a generic calculator depth.
Think through the full process before entering a single number. Are you replacing removed soil, adding a surface layer, filling new raised beds or improving already usable ground? Each case can require a different volume. Existing site soil that can be reused should be counted before you order imported material.
Divide an L-shaped space into two rectangles; measure a circular bed independently; measure separate raised beds using their internal dimensions. Where topsoil depth changes significantly, calculate shallow and deep zones separately. Add the volumes and then apply one clearly stated ordering allowance, rather than multiplying every estimate by several untracked safety factors.
Record your calculated cubic metres, intended use, proposed depth, bag size, delivery location and material specification. A supplier may sell by tonnes instead: use the approximate weight only as a conversation starter unless the seller provides an actual bulk-density conversion for the selected batch.
For substantial earthworks, major changes of level, retaining structures or potentially contaminated land, a measured survey and competent professional advice may be necessary. This Topsoil Calculator provides a practical ordering estimate, not an engineering design or soil laboratory report.
Multiply area in square metres by the required depth in metres. For example, 20 m² at a 100 mm layer uses 20 × 0.1 = 2 m³ before allowances.
At 100 mm depth, 20 m² requires 2 m³. At 150 mm, it requires 3 m³. Add an ordering margin only if it suits your measurements.
One cubic metre is exactly 1,000 litres. It also equals approximately 35.315 cubic feet or 1.308 cubic yards.
A common starting point is at least 100 mm of suitable topsoil where a new layer is required. The total prepared growing depth, underlying soil quality and drainage also matter.
There is no fixed weight. The calculator uses an illustrative 1.30 tonnes per m³ for screened topsoil, and lets you override that with the supplier’s stated bulk density.
No. Bulk bags are sold in several nominal capacities, including 750 L and 1,000 L. Check the actual contents shown in the product listing.
Twenty-five full 40 L bags make 1,000 litres, which is one cubic metre. This is before any extra ordering allowance.
Yes. Select Circular Planting Area and enter its diameter plus the required topsoil depth. The tool uses the area of a circle.
Yes, for identical planters. Enter the internal dimensions and count. For planters with different sizes, calculate each separately and add the volumes.
Ordering margin covers measuring uncertainty and minor waste; a settlement allowance covers possible reduction in volume after placing. Avoid counting the same uncertainty twice.
Yes. Select Imperial and use feet for lengths, inches for depth, square feet for area or cubic feet for an existing volume. The tool converts them internally.
Yes, if you enter your own bag price or bulk price per cubic metre. Prices are shown as alternatives and may not include delivery or VAT.
No. It estimates volume and approximate weight. Request suitable product and testing information for your intended use.
Yes. Once you calculate a valid result, you can copy a text summary or download a locally generated PDF without uploading the input data.
Continue planning other parts of your garden or building project with these related ConstructionMath calculators. Use separate material estimates for aggregate, ballast and concrete rather than treating those materials as suitable substitutes for topsoil.
Methodology: geometric volume; 1 m³ = 1,000 L = approximately 1.30795 yd³; default ordering margin 10% and extra settlement 0%; density assumptions are illustrative only. Gardening guidance: RHS Topsoil Buying and RHS How To Make A Raised Bed. Standards and soil suitability: BS 3882:2015 and local authority site assessment guidance. Reviewed November 2026.