Gardeners Toolkit
Free UK landscaping calculator

Gravel Calculator

Work out the volume of gravel or decorative stone you need, then convert it into an approximate weight and real bag quantities using the figures from your supplier.

Multiple areasEditable densitySmall & bulk bags
Diagram showing a measured garden path, gravel layer depth and bulk bag conversionmeasured areadepthsupplierbag size

Calculate volume first. Convert to weight second.

Gravel is spread by volume, but many suppliers sell it by weight. Those are not interchangeable without a density assumption. This calculator keeps the three stages separate: measured volume, estimated weight and product packaging.

Using decorative stone or chippings?

Use this same calculator. The underlying area × depth calculation is the same, while the density and bag figures can be changed to match the actual product you are buying.

Calculate your gravel requirement

Choose how you know the main area, add any extra zones, then set the finished gravel depth and supplier figures.

Depth help
Step 1

Measure the area

Extra measured areasAdd paths, beds or sections you already know in m².

For complicated curves or cut-outs, measure once with the Garden Area Calculator, then enter the total area here.

Step 2

Set depth and material assumptions

Examples only — stone size and use affect the required depth.
kg/m³
Editable estimate. Use your supplier's density/coverage data where available.
%
Step 3

Match the product packaging

kg
kg
L

Bag sizes vary widely between products and suppliers. Current UK gravel retailers list bulk bags around 500kg, 800kg, 850kg, 875kg and 1000kg, so the fields stay editable.

Your gravel estimate

Base volume required—

Volume is the geometry result. Weight and bag counts depend on the editable assumptions below.

Project area—
Litres—
Estimated weight—
Small bags—
Bulk bags by weight—
Volume with allowance—
—

Planning the whole gravel area?

Once you know the quantity, these tools help with the parts of the job that usually come next.

Choose a sensible depthCompare decorative areas, paths and stone sizes before ordering.Measure membraneAllow for roll width and overlap under suitable gravel areas.Calculate edgingWork out the linear edge needed to contain the finished surface.Comparing gravel with paving?Estimate slab quantities for the same measured area.

How the gravel calculation works

Volume = area × depth. Convert the depth to metres first. Estimated weight = volume × the density you enter.

For a 10m × 5m area at 50mm deep, the area is 50m² and the depth is 0.05m. The base volume is therefore 2.5m³, or 2,500 litres. At an example density of 1,600kg/m³ that would be approximately 4,000kg. Change the density if your product data says otherwise.

Cross section showing gravel depth over a basedepthgravel layerprepared baseDepth changes quantity quicklyDoubling depth doubles the gravel volume for the same area.
Diagram showing volume converted into estimated weight and bagsm³volumekgdensitybagsDo not confuse volume with weightStone type, grading and moisture can change bulk density, so supplier data beats a generic estimate.

What gravel depth should you enter?

There is no universal depth. Current UK supplier guidance varies with aggregate size and intended use. Gravelmaster, for example, suggests around 30–40mm for some 10mm aggregates and 40–50mm for some 20mm aggregates, with greater depths for driveways. Stone Warehouse uses 50mm for many gravel/chipping products up to 20mm and deeper layers for larger pebbles. Treat those as supplier examples, not engineering rules.

Use the dedicated gravel depth guide to choose a planning depth, then confirm the recommendation for the actual product and build-up.

Why bag coverage is never universal

Retail packaging is one of the biggest sources of bad gravel estimates. A “bulk bag” is not a standard unit of volume or weight. Current UK product listings show materially different bag weights even within one supplier. This calculator therefore asks for the bag weight you are actually buying rather than hard-coding a single figure.

Common gravel-calculator mistakes

  • Using 50 instead of 0.05 metres in the volume formula. A 50mm layer is 0.05m deep.
  • Assuming a tonne always covers the same area. Coverage changes with depth and material density.
  • Using a bulk-bag label from another product. Enter the actual bag weight or volume from your supplier.
  • Ignoring separate garden zones. Measure each path or bed section and add the areas rather than estimating one bounding rectangle.
  • Treating decorative gravel as the whole construction build-up. A path or driveway may need a suitable sub-base and drainage design beneath the decorative layer.
Planning sources used for this page

Depth and packaging examples were checked against current UK supplier tools from Gravelmaster, Stone Warehouse and Mainland Aggregates. Product-specific supplier guidance should override generic defaults.

Check the depth & volume referenceVerify litres per square metre and area × depth conversions.