How much gravel do I need?

Multiply the area by the depth to get the volume in cubic metres, then multiply by the density to get tonnes. Gravel is usually around 1.5 tonnes per cubic metre. The calculator works out both from the area and depth you enter.

How deep should gravel be?

A path is often 50 mm deep, while a driveway is usually 75 to 100 mm or more over a compacted base. Deeper layers need more material. Enter the depth in millimetres for your job.

How many tonnes in a cubic metre of gravel?

Most gravel and crushed metal weighs about 1.5 tonnes per cubic metre, though it varies with the stone and how wet it is. The calculator lets you change the density if your supplier gives a different figure.

Gravel Calculator

This calculator works out how much gravel, metal or aggregate to order for a driveway, path, base course or drainage layer, so you can buy close to the right amount instead of guessing and either running short mid-job or paying for material you never use. You enter the area you need to cover in square metres, the depth you want to lay it in millimetres, and the density of the material in tonnes per cubic metre, which defaults to 1.5 but can be changed to match the figure your quarry or landscape supplier gives you for the specific gravel, metal or aggregate you are buying. From those three figures the calculator instantly returns the volume in cubic metres and the total weight in tonnes, which is how most New Zealand suppliers price and deliver bulk gravel. Because paths and driveways are rarely a single neat rectangle, measure and add up the area of each section separately before you enter a total, and remember that a driveway base is usually laid deeper than a garden path. It is also worth ordering a bit extra beyond the calculated figure, since gravel compacts and settles once it is spread, driven on and rained on, so the finished depth ends up shallower than what you first laid. These are quantity estimates only; always confirm final volumes with your supplier before ordering.

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Area (m²)

Depth (mm)

Density (tonnes per m³)

0 t

gravel needed

Volume0 m³

Order a little extra to allow for compaction and settling.

How it works

The volume is the area times the depth, with the depth converted from millimetres to metres. Multiply the volume by the density to get the weight in tonnes. Suppliers often sell by the cubic metre or by the tonne, so the calculator shows both.

Worked example

For 20 square metres at 75 mm deep, the volume is 20 times 0.075, which is 1.5 cubic metres. At 1.5 tonnes per cubic metre that is about 2.25 tonnes of gravel.

Related calculators

Concrete Calculator: concrete volume.
Cubic Metre Calculator: work out a volume.
Topsoil Calculator: soil for a garden.
Mulch Calculator: mulch for beds.

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