Gravel Calculator

Gravel Calculator works out the weight of aggregate a path, drive or border needs, because gravel is sold by the tonne and spread by the square metre. The bridge between the two is density, which differs by material: gravel is about 1,600 kg per cubic metre, hardcore about 2,000 and slate chippings about 1,300.

Depth depends on the job. Four to five centimetres is right for a decorative path or border -- deep enough to cover and shallow enough to walk on. A drive needs the same decorative layer over a compacted sub-base of 100 to 150 mm of hardcore, which is a separate calculation with a different material.

The coverage-per-tonne figure is the one to take to a supplier. At five centimetres deep, a tonne of gravel covers about twelve and a half square metres; at ten centimetres it covers half that. Suppliers quote coverage at a stated depth, and checking it against your own depth is how you avoid ordering twice.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

• Shows tonnes needed, volume, bulk bags, small bags (25 kg) and cost together, so you are not running it twice
• A results table you can read across
• Updates as you type, with no button to press and no page reload
• Copy the result in one click
• Free, no sign-up, and it runs entirely in your browser

The gravel calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Ordering gravel for a path or driveway
• Working out hardcore for a sub-base
• Converting tonnes into bulk bags
• Checking a supplier's coverage claim