Gravel calculator
Estimate gravel for paths, driveways, decorative areas or drainage: area, depth, density, waste, tonnes, bags, bulk bags and budget.
This choice applies to every calculator; amounts are not converted.
Gravel calculation
Calculate gravel volume and weight, then convert the requirement into bulk, bulk bags or bags.
Price and supply
Supply
Weight actually purchased
Surplus
Added allowance
Estimated budget
Calculation details
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How does this tool work?
The gravel calculator turns an area and a depth into a volume, then into a weight to order. It takes into account the density of the material, an allowance for compaction or site losses, and the way the gravel is actually sold: loose in bulk, in bulk bags or in small bags.
The area comes from length × width, or you type it in directly.
The depth, entered in centimetres, is converted to metres and multiplied by the area to give the raw volume in m³.
The allowance is added to that volume, then the density in t/m³ converts it into tonnes to order. Choosing a use or a gravel type pre-fills a typical depth or density, which you can overwrite.
For bags and bulk bags, the weight required is divided by the weight of one package and rounded up, so the purchased weight and the surplus are shown separately. The optional price is applied to bulk tonnes or to the number of packages.
Tonnage depends on both volume and the selected bulk density, so equal volumes of different gravel can have different weights. Compare the target compacted depth with delivery conditions because loose material and a compacted layer are not equivalent.
How to use this tool
Define the area
Dimensions or an area you already know.
Choose the use
The calculator suggests a starting depth that you can change.
Adjust the material
Pick an indicative density or enter your supplier’s value.
Prepare the order
Bulk, bulk bag or bags, with an optional price.
Gravel formulas
The weight depends directly on the real density of the material.
Volume
V = area × depth
The depth must be converted to metres.
Weight
M = volume × density
With a density in t/m³, the result is in tonnes.
Allowance
order V = V × (1 + allowance / 100)
The allowance can cover compaction, levelling and small losses.
The suggested depths and densities are indicative. Grading, sub-base, compaction and installation requirements can change the quantities needed. Use the density given by your supplier when it is available.
Use cases
Footpath
Estimate the gravel needed from the area and a depth suited to your project.
Driveway
Plan a larger volume and weight with an adjustable depth; the sub-base is sized separately.
Decorative gravel
Work out bags or bulk bags for a courtyard, a patio or flower beds.
Drainage
Estimate a large volume of drainage gravel from the area and depth of the trench or bed.
Examples
8 × 5 m footpath delivered in bulk
40 m² × 0.05 m = 2 m³, plus 5% = 2.1 m³, and 2.1 × 1.5 = 3.15 t.
Input
8 m × 5 m · 5 cm depth · density 1.5 t/m³ · 5% allowance · bulkResult
Raw volume 2 m³; volume required 2.1 m³; 3.15 t to order40 m² driveway in bulk bags
40 × 0.08 = 3.2 m³, plus 5% = 3.36 m³, × 1.6 = 5,376 kg: six full bulk bags are needed.
Input
Area 40 m² · 8 cm depth · crushed limestone 1.6 t/m³ · 5% allowance · 1,000 kg bulk bagsResult
3.36 m³; 5.38 t; 6 bulk bags (6,000 kg bought, 624 kg surplus)12 m² decorative bed in bags
12 × 0.04 = 0.48 m³, plus 5% = 0.504 m³, × 1.5 = 756 kg. 756 ÷ 25 = 30.24, rounded up to 31 bags.
Input
Area 12 m² · 4 cm depth · density 1.5 t/m³ · 5% allowance · 25 kg bagsResult
0.5 m³; 756 kg; 31 bags (775 kg bought)Tips and best practices
- Density varies with the rock, the grading and the moisture content: your supplier’s data sheet is the best reference.
- For a driveway, the gravel layer is only part of the build-up: the sub-base must be sized separately.
- For a bulk delivery, check the access for the lorry and where the load can be tipped.
Sources and references
Frequently asked questions
How much does 1 m³ of gravel weigh?
It depends on the material. A common indicative range is around 1.5 to 1.7 tonnes per m³, but use your supplier’s density for an accurate estimate.
How deep should the gravel be?
It depends on the use, the sub-base and the grading. The calculator suggests a starting value you can change, not a structural specification.
How do I convert cubic metres of gravel into tonnes?
Multiply the volume in m³ by the density in tonnes per m³: 2.1 m³ at 1.5 t/m³ is 3.15 tonnes.
Why add an allowance?
It can cover compaction, levelling, small losses or differences on site. It is applied to the volume before converting to weight.
Can the calculator give me a number of bags?
Yes. Choose Bag and enter the weight of one bag. The result is rounded up to the next bag, and the purchased weight and surplus are shown separately.
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