Landscaping
Gravel Calculator
Enter the area dimensions in metres and the gravel depth in millimetres to get the cubic metres and tonnes to order, with wastage and an optional VAT-aware cost estimate.
Formula tested · Local units · No sign-up
Project inputs
Enter measurements
Use your preferred units. Results update automatically.
Show the calculation methodFormula, conversions, rounding, and assumptions+
Volume = length × width × depth, with depth converted from millimetres to metres first — a 100 mm layer over 5 m × 4 m is 5 × 4 × 0.1 = 2 m³.
UK aggregates may be sold loose by the tonne or in product-specific bags. The calculator converts volume using the density you enter and rounds only when you enter the current quote's tonne increment.
Real-world example
Worked example: 5 m × 4 m driveway topping, 100 mm deep
- Convert depth: 100 mm = 0.1 m.
- Volume: 5 × 4 × 0.1 = 2.0 m³.
- For this example, enter a 5% allowance: 2.0 × 1.05 = 2.1 m³.
- Enter the example density of 1,680 kg/m³: 2.1 × 1,680 = 3,528 kg = 3.528 tonnes. Replace it with the selected product's density.
- Enter the example supplier increment of 0.25 tonne: 3.528 rounds up to 3.75 tonnes.
The example order is 3.75 tonnes only with the entered 5% allowance, 1,680 kg/m³ density and 0.25-tonne quote increment.
Before you start
How to measure
- Measure the area in metres and the depth in millimetres; for a gravel drive over sub-base, only measure the depth of the decorative layer here and run the sub-base (MOT Type 1) as a separate calculation.
- A 50 mm layer of 20 mm gravel is a common decorative depth; anything trafficked needs a proper compacted sub-base underneath.
- For borders around a house, subtract the building footprint rather than measuring lots of thin strips.
Local guidance
Notes for United Kingdom
- UK gravel is sold loose by the tonne, in bulk bags (fills vary — often labelled by weight around 800 kg to a tonne; check the product) and in 25 kg small bags for patch jobs.
- Decorative gravels (pea shingle, golden gravel, slate chippings) have different densities — slate in particular differs from rounded gravel, so use the supplier's tonnage guidance for the specific stone.
- VAT at the standard 20% rate applies to aggregate supply; trade and quarry quotes are often ex-VAT, so check before comparing.
Quick reference
Gravel depth quick reference (typical planning values)
| Application | Common depth |
|---|---|
| Decorative borders over membrane | 40–50 mm |
| Garden paths | 50 mm |
| Driveway topping (20 mm gravel) | 50 mm over compacted sub-base |
| Sub-base under drives (separate material) | 100–150 mm compacted |
Planning values only — a gravel drive is only as good as the sub-base beneath it.
Good to know
Common mistakes to avoid
- Typing depth in centimetres into a millimetre field — 5 instead of 50 gives a tenth of the gravel.
- Assuming a bulk bag holds exactly a tonne — fills vary by supplier and stone; check the stated weight.
- Using rounded-gravel density for slate chippings or other flat stone, which covers differently.
- Ordering the decorative layer and the sub-base as one material — they're different products at different prices.
Need help?
Frequently asked questions
How many tonnes for a 3 m × 2 m path at 50 mm?
3 × 2 × 0.05 = 0.3 m³. If you enter a 5% allowance and a density of 1,680 kg/m³, that becomes about 0.529 tonnes. It rounds to 0.75 tonnes only if the current supplier quote uses a 0.25-tonne increment.
How many tonnes is a cubic metre of gravel?
At an entered density of 1,680 kg/m³, one cubic metre converts to 1.68 tonnes. That is an arithmetic example, not a default; use the supplier's figure for the exact product and condition.
Should I buy loose, bulk bags or 25 kg bags?
Loose by the tonne is usually the cheapest per kilogram for larger jobs; bulk bags suit mid-size jobs and tight access; 25 kg bags only make sense for small patches. Compare using the tonnage this calculator shows and your supplier's prices.
Keep planning
Related calculators
Measure with confidence
Planning guides for this project
Transparency
About this calculator
- Written by:
- BuildMeasure Editorial Team
- Technically reviewed by:
- Pending independent technical reviewer (formula unit-tested; see methodology)
- Last reviewed:
- 2026-07-23
- Formula version:
- 1.1.0
- Region reviewed for:
- United Kingdom
- Spotted an error?
- Report a correction
Methodology
- Volume is computed as length × width × depth, converted internally to SI units (metres) before any arithmetic to avoid unit drift.
- The optional wastage allowance is applied to exact finished volume for handling and uneven spreading. It is not a loose-to-compacted conversion; obtain that separately for the selected aggregate and method.
- Weight = total volume × the bulk density you enter for the exact product and condition. No default density is supplied because stone type, grading, moisture and loose or compacted state change the conversion.
- Supplier rounding occurs only when you enter the mass increment shown on the current quote. If the increment is blank, the calculator reports the unrounded calculated weight.
- The preliminary material subtotal multiplies calculated or supplier-rounded weight by the price you enter. Tax is added only after you confirm that the entered price excludes tax and provide a rate; an unresolved basis does not produce a final total.
- The formula is covered by automated unit tests, including hand-calculated worked examples, and is versioned (see formula version on this page).
Sources & standards
- Unit definitions: 1 tonne = 1,000 kg; metric units throughout.
- Density boundary: Weight is calculated only from the entered supplier density; no universal density or quarter-tonne sale increment is assumed.
This tool provides a material estimate for planning purposes only. It is not a quotation, and the weight conversion depends on the density you enter — stone type and moisture change it. Confirm quantities and density with your supplier before ordering.