1. Your project measurements
Enter the area to cover and your intended material depth. Depths and densities are examples, not construction specifications.
For irregular shapes, use an equivalent measured area (for example, enter the area in m² as the length and set width to 1 m). Allowance is applied to volume before estimating tonnes.
2. Aggregate assumptions
Supplier bulk-bag weights vary. Confirm the actual bag contents and material density before ordering. MOT Type 1 may require a compaction allowance not modelled here.
3. Compare buying options
All prices are editable placeholders, not live supplier quotations. Loose loads may have minimum quantities, vehicle-access restrictions and unloading requirements.
Your gravel estimate
Bulk bags
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Loose delivery
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Before ordering: This is a material estimate, not a supplier quote or a recommendation for layer depth. Check density, bag weight, delivery terms, minimum loose-load order and whether your project needs compaction. Loose delivery assumes the supplier will sell the exact calculated tonnage.
Printable shopping list
Totals are illustrative material and entered delivery costs only; labour, preparation, membrane, edging, plant hire and VAT differences are excluded.
How to estimate gravel for a UK garden project
Start by measuring the area in metres. Multiply length by width to get square metres. Multiply that area by the planned depth in metres to get cubic metres. The calculator adds your chosen allowance, then multiplies by the editable bulk density to estimate tonnes.
Worked example
A 5 m × 3 m path at 50 mm depth covers 15 m² and has an initial volume of 0.75 m³. With 10% extra allowance and an assumed density of 1.6 t/m³, the estimate becomes 1.32 tonnes, or two 0.8-tonne bulk bags.
Buying loose or bagged?
Bulk bags are often convenient for smaller projects and where delivery space is limited. Loose loads may be economical for larger quantities, but suppliers may apply minimum-load and delivery charges. Compare actual quotes before buying.
Before you order
- Confirm the material. Decorative gravel, shingle and compactable sub-base have different uses and densities.
- Confirm the depth. The appropriate depth depends on the project and supplier guidance; don't treat the example as a specification.
- Check the supplier's units. A bulk bag may be sold by weight, nominal volume or another description.
- Check site access. Loose aggregate deliveries need a suitable unloading area; bulk bags also need appropriate delivery access.
Common questions
How many bulk bags of gravel do I need?
Divide estimated tonnes by the weight in each bag and round up to whole bags. Check the actual weight stated by the supplier.
Is one tonne the same as one cubic metre?
No. Tonnes measure mass and cubic metres measure volume. The conversion depends on the aggregate's bulk density.
Does the calculator include compaction?
Not separately. The editable extra allowance can help with uncertainty, but it is not a compaction model. For compacted layers, use the supplier's guidance on loose quantities and compaction factors.
Is loose gravel always cheaper?
No. It depends on delivery fees, minimum orders, supplier pricing and access. The comparison uses only the prices you enter.
Worked bulk-bag versus loose-delivery example
Example: a 5 m × 3 m area at 50 mm depth. The starting volume is 0.75 m³. With 10% extra allowance, that becomes 0.825 m³. At an illustrative 1.6 tonnes per m³, you need about 1.32 tonnes, or two bags if each contains 0.8 tonnes.
Compare like with like: two bags at £75 each cost £150 before any bag delivery. A loose price of £45 per tonne plus £40 delivery gives £99.40 for 1.32 tonnes, but the supplier may charge for a minimum order. Enter actual supplier quotes above.
Read the gravel buying guide for density, bag weight and delivery checks.