Gravel Calculator FAQ

It depends on the project. Decorative borders can often be estimated with a shallower finished depth than paths, while driveways and bases need separate checks for sub-base, drainage, and compaction. Use the calculator to compare depths, then confirm the build-up for load-bearing work.

Yes, a small allowance is sensible for settlement, measuring errors, edging losses, and small spills. The calculator uses a 10% allowance. For awkward shapes, uneven ground, or long edges, check whether a larger allowance is prudent before ordering.

Yes. The result shows volume in cubic metres and cubic yards, and weight in tonnes and US tons, so you can order in either metric or US-customary units.

Enter the supplier's bulk bag weight in the bag size field. For example, use 850 if the bag is listed as 850 kg. The calculator divides the estimated kg by that bag weight and rounds up to the next whole bag.

The area and depth give volume, but many suppliers sell by weight. Density converts cubic metres into tonnes or kg. Pea gravel, slate chippings, cobbles, and sub-base materials can have different densities, so supplier data should replace the default when available.

You can use it as a quantity estimator by choosing the MOT Type 1 preset or entering a custom density, but calculate sub-base layers separately from decorative gravel. This calculator does not decide the correct structural build-up for a driveway, patio, or base.

Split the area into rectangles where possible, calculate each area, and add them together. For curves, use an average width and add a sensible allowance. Exclude fixed features such as steps, drains, planters, and paving that will not be covered.

Coverage estimates depend on depth, aggregate density, bag weight, moisture, and how full a bulk bag is. A supplier quote at 3 cm depth is not comparable with your project if you plan to lay 5 cm or 7.5 cm.

Small bags are convenient for small borders and touch-up jobs. Bulk bags or loose delivery usually make more sense for larger areas, but check delivery access, drop-off location, handling effort, and the exact bag weight before comparing prices.

Use it to estimate the visible gravel or selected aggregate layer, not as driveway construction advice. Driveways may need a compacted sub-base, edge restraints, drainage, and a project-specific depth.