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 are sold loose by the tonne or in bulk bags, so the volume is converted to weight using the density you enter (default 1,680 kg/m³, a typical value for compacted gravel — check your supplier's figure) and rounded up to the next quarter tonne.
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.
- Add 5% wastage: 2.0 × 1.05 = 2.1 m³.
- Convert to weight at 1,680 kg/m³: 2.1 × 1,680 = 3,528 kg = 3.528 tonnes.
- Round up to the ordering increment: 3.75 tonnes.
Order 3.75 tonnes. At an example price of £30 per tonne plus 20% VAT, that's £112.50 + £22.50 = £135.00.
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. With 5% wastage that's 0.315 m³, which at 1,680 kg/m³ weighs about 529 kg = 0.53 tonnes — the calculator suggests ordering 0.75 tonnes, or you could make up the quantity with bulk bags.
How many tonnes is a cubic metre of gravel?
At the default density of 1,680 kg/m³, one cubic metre weighs 1.68 tonnes. Loose decorative gravels can be lighter and damp stone heavier — use your supplier's figure for the specific product.
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.
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About this calculator
- Written by:
- BuildMeasure Editorial Team
- Technically reviewed by:
- Pending independent technical reviewer (formula unit-tested; see methodology)
- Last reviewed:
- 2026-07-16
- Formula version:
- 1.0.0
- 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 wastage allowance is applied to the exact volume to cover compaction, settling and spreading losses.
- Weight = total volume × density. The density default of 1,680 kg/m³ is a clearly-labelled typical value for compacted gravel and is fully editable — actual density varies with stone type, size and moisture, so use your supplier's figure.
- Because gravel is usually sold by weight, the suggested order rounds the weight UP to the next 0.25 of the regional selling unit (US short tons in the US, metric tonnes elsewhere).
- The cost estimate simply multiplies the suggested order weight by the price you enter, then applies the tax rate you enter. No prices are built in.
- 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 default: 1,680 kg/m³ is a typical planning value for compacted gravel — editable; decorative stone varies, check your supplier's figure.
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.