How do I convert cubic metres of gravel to tonnes?

Multiply the volume in cubic metres by the material bulk density in tonnes per cubic metre. For most loose gravels that density is about 1.5, so one cubic metre weighs roughly 1.5 tonnes.

What depth of gravel should I use?

A decorative gravel path or border is usually 4 to 5 cm deep. A gravel driveway that carries cars needs a compacted sub-base plus about 5 cm of top gravel, so total depth is greater.

Gravel compacts under its own weight and traffic, and ground is rarely perfectly level, so ordering about 10 percent more than the theoretical volume avoids a second delivery.

What is the Gravel Tonnage Calculator?

Calculate how many tonnes of gravel, aggregate or sub-base you need from an area, depth and bulk density. Also shows cubic metres and equivalent bags. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Gravel Tonnage Calculator

Name: Gravel Tonnage Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Gravel is quoted by weight when delivered loose but measured by volume when you plan a job, so you need to convert between the two. This calculator turns an area and a target depth into cubic metres, then into tonnes using the bulk density of your material.

How it works

area   = length × width
volume = area × (depth in cm / 100)
tonnes = volume × bulk density

Bulk density is the weight of a cubic metre of the loose material. Most decorative gravels and crushed-stone sub-bases sit around 1.5 to 1.6 tonnes per cubic metre, which is why the field defaults to 1.5 — but sand, ballast and MOT type-1 differ, so adjust it to match your supplier’s figure.

Worked example

A 5 m × 3 m area at 5 cm deep, using a density of 1.5:

Area = 15 m²
Volume = 15 × 0.05 = 0.75 m³
Weight = 0.75 × 1.5 = 1.13 tonnes

What to watch

Compaction means a driveway needs more than the bare volume suggests — order about 10 percent extra so you are not short after the surface beds in.

Sub-base is separate. A driveway that carries vehicles needs a compacted sub-base layer beneath the decorative gravel. Calculate each layer separately and add them.