Cubic metres
Length × width × depth, all in metres, gives cubic metres. A 5 × 4 m patch at 5 cm deep is 5 × 4 × 0.05 = 1 m³ before any extra.
Gravel Calculator UK: How Much Gravel Do I Need?
Measure each part of the job, enter a depth, and get the tonnes, cubic metres and bags to order.
Last updated Math checked by 19 automated testsSee every formula
Your areas
Not sure how deep? Typical depths
| Project | Depth people commonly use |
|---|---|
| Decorative beds and borders | 5-8 cm (2-3 in) |
| Garden paths | 5-8 cm; 8-10 cm if wheelbarrows use it |
| Patios and seating areas | 8-10 cm (3-4 in) |
| Driveways | Two layers: compacted MOT Type 1 and a top layer. Use the driveway calculator |
| Under paving, sheds or slabs | Whatever the manufacturer or your plans say |
Starting points, not specifications. Soil, traffic and frost change the right answer, so check with your supplier or installer.
Material and extra allowance
Fills in a typical value so you get tons straight away. It varies by quarry and moisture, so replace it with your supplier's figure when you have it.
Only needed for tons. Ask the yard for the weight of the exact product, because stone type and moisture change it. How to find it, or weigh a bucket yourself.
Base stone such as crusher run packs down when it is rolled, so you need more loose stone than the finished depth. Your supplier can tell you how much to add.
Prices and delivery optional
Fill in whichever prices you have. Each way of buying is shown as its own total, with delivery added to each. VAT and labour are not included.
Gravel coverage calculator: how far will it go?
Already have a pile or a quote? Enter the amount and find out how much ground it covers, or how deep it will be over an area you know.
Enter an amount and a depth to see the coverage.
How the gravel calculator works
Each area is surface area times depth. The areas are added up, then your compaction and waste percentages are added on top of that measured total. Weight uses only the density you enter, so it matches what your supplier will weigh.
- Rectangle
- length × width × depth
- L-shape
- (length × width − notch length × notch width) × depth
- Circle
- π × (diameter ÷ 2)² × depth
- Triangle
- base × height ÷ 2 × depth
- Trapezoid
- (long side + short side) ÷ 2 × distance between × depth
- Known area
- area × depth
Gravel in tonnes, cubic metres and square metres
Tonnes
Merchants usually sell loose gravel by the tonne or in bulk bags. Tonnes = cubic metres × density in kg/m³ ÷ 1,000. Use the merchant's figure, because stone type and moisture change it.
Square metres
Already know the area? Pick "Known area" and enter square metres plus a depth. One cubic metre covers 20 m² at 5 cm deep, or 10 m² at 10 cm.
How many tonnes are in a cubic metre of gravel?
It depends on the stone. Tonnes = cubic metres × density in kg/m³ ÷ 1,000. At 1,600 kg/m³ a cubic metre weighs 1.6 tonnes, so a tonne is about 0.63 m³.
| Density (kg/m³) | Tonnes per m³ | m³ per tonne |
|---|---|---|
| 1,400 | 1.4 | 0.71 |
| 1,500 | 1.5 | 0.67 |
| 1,600 | 1.6 | 0.63 |
| 1,700 | 1.7 | 0.59 |
| 1,800 | 1.8 | 0.56 |
Convert any amount between tonnes, cubic metres, yards and tons
How much area does a cubic metre cover?
Only the depth matters: square metres covered = 1 ÷ depth in metres.
| Depth | Square metres per m³ |
|---|---|
| 2.5 cm | 40 |
| 5 cm | 20 |
| 7.5 cm | 13.3 |
| 10 cm | 10 |
| 15 cm | 6.7 |
How many bulk bags of gravel do I need?
Divide your weight by what one bag holds. Bulk bags are usually somewhere between 800 kg and 1 tonne depending on the merchant, so check the label. At 850 kg a bag, 3 tonnes is 3.53 bags, so order 4.
| Bag | Weight | Bags per tonne |
|---|---|---|
| Small bag | 20 kg | 50 |
| Small bag | 25 kg | 40 |
| Bulk bag | 850 kg | 1.18 (round up) |
| Bulk bag | 1 tonne | 1 |
The calculator counts 25 kg bags and 850 kg bulk bags once you add a density. If your merchant's bulk bag is a different weight, divide the tonnes by that weight instead.
How much gravel fits in a tipper lorry?
It depends on the lorry, so ask the merchant how much one load carries. Enter that in "One lorry load holds" and the calculator counts the loads, rounded up.
- Get your total in tonnes or cubic metres from the calculator.
- Ask the merchant what one load carries and whether there is a minimum order.
- Enter the load size and the delivery charge under Prices and delivery.
- Compare the loose load with bulk bags before you order.
Worked example: gravel for a patio and a path
- Patio: 4 m × 3 m = 12 m². At 10 cm (0.1 m) that is 1.2 m³.
- Path: 8 m × 1 m = 8 m². At 5 cm (0.05 m) that is 0.4 m³.
- Measured total: 1.2 + 0.4 = 1.6 m³.
- Add 10% waste: 1.6 × 1.10 = 1.76 m³.
- At a density of 1,600 kg/m³: 1.76 × 1,600 = 2,816 kg, or 2.82 tonnes.
- In 850 kg bulk bags: 2,816 ÷ 850 = 3.31, so 4 bags.
Enter the patio and the path as two areas above and the calculator does every step, including the bag count.
Gravel for driveways, patios, pavers and drains
The math is the same for every job. What changes is the depth and the shape, so measure each part separately and add it as its own area.
Driveway gravel
A driveway is usually a compacted base layer under a thinner top layer, each a different stone. The driveway calculator takes both layers, their compaction and their prices.
Pea gravel
Pea gravel is a loose cover for paths, patios and play areas. Use the finished depth you want and the density your supplier lists for pea gravel.
Paver base
Enter the paver area and the base depth from the paver maker or your installer. Add compaction, because the base is plate-compacted and shrinks.
French drain
A drain trench is a long rectangle with a pipe in it. The French drain calculator takes the pipe's volume out so you do not over-order.
Under a concrete slab
Enter the slab footprint and the base depth from your plans or local building guidance. This is a quantity estimate only, not a structural check.
L-shaped and curved areas
Use the L-shape for a patio that wraps a corner, the trapezoid for a tapering bed, and split anything curvy into a few simple shapes.
Common types of gravel in the UK
Names vary between merchants, so confirm the product and its weight before you order. The calculator works the same for all of them.
| Material | What it is | Typical uses |
|---|---|---|
| 10mm or 20mm gravel | Washed, rounded or angular stone graded to size | Driveway top layer, paths, borders |
| Pea shingle | Small rounded stones, around 6-10 mm | Paths, play areas, pots and beds |
| MOT Type 1 | Crushed stone with fines that compacts hard | Sub-base for driveways, patios and paving |
| Slate chippings | Flat slate pieces in blue, plum or green | Decorative beds and borders |
| Self-binding gravel | Fine gravel that sets firm when rolled and wetted | Paths and patios that need a firm surface |
| Sharp sand | Coarse washed sand | Bedding paving, mixing with cement |
Gravel calculator FAQ
How much gravel do I need?
Measure each area in metres, pick a depth, and multiply length × width × depth to get cubic metres. Multiply by the density in kg/m³ and divide by 1,000 for tonnes. This calculator does that for several areas at once.
How many tonnes of gravel are in a cubic metre?
Usually somewhere around 1.5 to 1.7 tonnes for loose gravel, but it depends on the stone and moisture. Use the merchant's figure for the exact product.
How much does a bulk bag of gravel cover?
An 850 kg bag at 1,600 kg/m³ is about 0.53 m³. Spread 5 cm deep that covers roughly 10.6 m²; at 2.5 cm, about 21 m².
How deep should gravel be on a driveway?
A common build is a compacted MOT Type 1 sub-base, often 10-15 cm, with 4-5 cm of 20mm gravel on top. Soft ground or heavy vehicles need more. Use the driveway calculator to work out both layers.
How much extra gravel should I order?
Many people add 5 to 10 percent for uneven ground and spillage. MOT Type 1 that will be compacted needs more on top of that; ask your merchant.
Is it cheaper to buy loose gravel or bulk bags?
Loose loads are usually cheaper per tonne for bigger jobs if the lorry can tip close by. Bulk bags are easier where access is tight. Enter both prices and the calculator shows each total.
How accurate are the material weights?
They are typical ranges, not exact figures. The calculator shows tonnes as a range and lets you replace the density with your merchant's number.
About this calculator
A free, independent planning tool. Everything runs in your browser using standard geometry and exact unit definitions; nothing you type is sent anywhere. Results are estimates for ordering, not engineering advice.
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