Gravel calculator
Estimate decorative gravel volume and weight while keeping depth, density and allowance assumptions visible.
20 LAUNCH TOOLS
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When to use it
Use for a decorative gravel path, border or similar measured surface after the finished gravel depth and supplier product have been chosen. Calculate sub-base, drainage and other layers separately.
How it works
Volume = area × depth in metres. Estimated weight = volume × loose bulk density; the visible allowance is applied afterwards. The result is not rounded to a supplier's bag size or loose-load increment.
Worked example
Assume a measured 25 m² decorative path, a selected 40 mm finished gravel depth, a supplier density of 1.6 t/m³ and a 10% ordering allowance. Convert 40 mm to 0.040 m: 25 × 0.040 = 1.00 m³; 1.00 × 1.6 = 1.60 tonnes; 1.60 × 1.10 = 1.76 tonnes. If that supplier sells 800 kg bulk bags, 1.76 ÷ 0.80 = 2.2, so three bags would be the next whole-bag quantity; check the stated net bag weight and coverage rather than assuming all bulk bags are equal.
Measurement guidance
Finished surface area in square metres, decorative gravel depth in millimetres, the supplier's loose bulk-density figure in tonnes per cubic metre and a separate ordering allowance.
Buying and specification checks
The default 1.6 t/m³ is an editable planning assumption, not a universal density. The calculation assumes an even finished depth and does not design drainage, a driveway or a load-bearing build-up. Confirm the actual product density, bag weight or coverage and sale increment before ordering.
Measure the surface and check the delivery
The weight estimate becomes useful only when its layer, product and delivery assumptions match the job.
- Measure the finished gravel footprint. Split irregular areas into simple shapes, calculate them separately and exclude fixed features that will not be covered. Record the chosen finished depth rather than copying an excavation or sub-base depth.
- Keep decorative gravel separate from geotextile, edging, sub-base, drainage and any reinforcement system. A coverage estimate does not show whether the proposed build-up drains, carries vehicles or suits the ground; use a project-specific design or competent advice where those functions matter.
- Choose the exact gravel before converting volume to weight. Ask the supplier for the product's loose bulk density, stated bag weight or coverage, minimum loose-load quantity and sale increment. Treat 1.6 t/m³ only as the calculator's editable starting assumption.
- Plan access and unloading before ordering: check vehicle size, surface and overhead restrictions, drop position, whether bags can be lifted to the work area, safe manual handling and where loose material can be contained. Agree a measured allowance for uneven formation, cuts or losses without adding it twice.
Common mistakes
- Entering the full excavation or sub-base depth as decorative gravel depth
- Treating the default density as a specification for every gravel product
- Converting tonnes to bulk bags without checking the supplier's net weight and coverage
FREE TOOL AND PROJECT PACK
What the free calculator provides
The free calculator converts a measured decorative-gravel area, chosen finished depth, supplier-density assumption and visible allowance into volume and estimated tonnes. It does not round to a supplier's bag or loose-load increment or design the supporting build-up.
What the dedicated pack adds
There is no dedicated Gravel Project Pack. The closest relevant existing offer is the Garden Groundworks bundle for wider patio, small concrete-base and garden-drainage planning; buy it only if those broader records are useful to the project.
- Patio decisions, measurements, quantities, quote, delivery, preparation, laying and completion records.
- Concrete-base purpose, dimensions, quantities, access, delivery, pour and curing controls.
- Garden-drainage observations, route and destination decisions, constraints, permissions, quantities and maintenance records.
Three separate printable digital products (PDFs): Patio Project Pack v2, Concrete Base Project Pack v2 and Garden Drainage Project Pack v2. Immediate digital delivery with 90-day access; no subscription.
Practical FAQs
Can I use the same depth for gravel and sub-base?
No. Enter only the selected finished decorative-gravel depth here. Sub-base and other layers have different purposes, depths and densities and need separate quantities.
Is 1.6 t/m³ suitable for every gravel?
No. It is a visible starting assumption. Particle size, shape, moisture and product grading affect loose bulk density, so use the supplier's figure for the exact material where available.
How do I convert the result into bulk bags or a loose load?
Divide the estimated tonnes by the supplier's stated net tonnes per bag, then round up to a whole bag. For loose delivery, use the supplier's minimum quantity and increments. Confirm coverage and do not assume every product sold as a bulk bag has the same weight.
Does the calculator design a driveway or drainage layer?
No. It estimates decorative coverage from the inputs you choose. Ground conditions, drainage route, edge restraint, reinforcement, sub-base and load-bearing suitability need a separate project-specific design.
Planning guidance, not a quotation or a substitute for project-specific design and competent advice.