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 GST-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 75 mm layer over 10 m × 3 m is 10 × 3 × 0.075 = 2.25 m³.
Australian landscape yards sell gravel and crushed rock both per tonne and per cubic metre, so the calculator shows the volume and converts to weight using the density you enter (default 1,680 kg/m³, a typical value for compacted gravel — check your supplier's figure), rounding the tonnage up to the next quarter tonne.
Real-world example
Worked example: 10 m × 3 m driveway topping, 75 mm deep
- Convert depth: 75 mm = 0.075 m.
- Volume: 10 × 3 × 0.075 = 2.25 m³.
- Add 5% wastage: 2.25 × 1.05 = 2.3625 m³.
- Convert to weight at 1,680 kg/m³: 2.3625 × 1,680 = 3,969 kg = 3.97 tonnes.
- Round up to the ordering increment: 4 tonnes.
Order 4 tonnes. Enter your supplier's price per tonne — advertised consumer prices in Australia normally include 10% GST.
Before you start
How to measure
- Measure the area in metres and the depth in millimetres; for driveways, treat the road-base layer and the decorative topping as separate calculations.
- A 50–75 mm decorative layer is common for paths and garden areas; trafficked surfaces need compacted road base underneath.
- For long rural driveways, measure in sections where the width changes rather than averaging the whole run.
Local guidance
Notes for Australia
- Australian suppliers quote crushed rock, road base, scoria and decorative pebbles per tonne or per cubic metre — the calculator shows both so either quote works.
- Product names vary by state (e.g. 20 mm Class 2 or 3 road base, blue metal, cracker dust) and densities differ between them — ask your supplier for the tonnes-per-m³ figure for the exact product.
- GST is 10% and consumer prices are usually advertised GST-inclusive; trade or quarry-direct quotes may be ex-GST.
Quick reference
Gravel depth quick reference (typical planning values)
| Application | Common depth |
|---|---|
| Decorative pebbles over fabric | 40–50 mm |
| Garden paths | 50–75 mm |
| Driveway topping | 50–75 mm over compacted road base |
| Road base under driveways (separate material) | 100–150 mm compacted |
Planning values only — reactive soils and vehicle loads determine the real build-up.
Good to know
Common mistakes to avoid
- Typing depth in centimetres into a millimetre field — 7.5 instead of 75 gives a tenth of the material.
- Comparing a per-tonne quote against a per-m³ quote without converting (at the default density, 1 m³ ≈ 1.68 tonnes).
- Using the same density for scoria (much lighter) as for blue metal — always check the product's figure.
- Skipping wastage: compaction with a plate compactor absorbs several percent of the loose volume.
Need help?
Frequently asked questions
How many tonnes for a 6 m × 1.2 m path at 50 mm?
6 × 1.2 × 0.05 = 0.36 m³. With 5% wastage that's 0.378 m³, which at 1,680 kg/m³ weighs about 635 kg = 0.64 tonnes — the calculator suggests ordering 0.75 tonnes.
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. Scoria is much lighter and wet road base heavier — use your supplier's figure for the exact product when converting quotes.
Do I need road base under decorative gravel?
For anything that carries vehicles, yes — a compacted road-base layer does the structural work and the decorative layer sits on top. Run each layer through the calculator separately, since they're different products at different densities and prices.
Keep planning
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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:
- Australia
- 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; product densities vary widely, 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.