About the Gravel Calculator
Gravel is one of the easiest materials to lay and one of the easiest to order wrongly. Yards sell it by the ton or tonne, plans are drawn in feet or metres, depths are given in inches or millimetres, and nobody quite agrees on how much a cubic yard of stone weighs. Order too little and the path is patchy; order too much and a pile of stone sits on the drive for a year.
This gravel calculator takes the size of the area, the depth you want and the type of stone, and gives the answer the way suppliers sell it: weight in tons or tonnes, with the volume in cubic yards or cubic metres alongside, the number of bags or bulk bags, and an optional cost. It works for rectangles and circles, and it warns you when the depth is too thin for the job.
How to Use the Gravel Calculator
Choose feet and inches or metres and millimetres.
Pick the shape of the area. For a rectangle, enter the length and width; for a circle, enter the diameter. Split an L-shaped or irregular area into rectangles and add the results.
Enter the depth of gravel in inches or millimetres.
Choose the material. Pea gravel, crushed stone and a compacted sub-base weigh different amounts for the same volume.
Leave the waste allowance at 5% unless the ground is very uneven.
Optionally, enter the price per ton or tonne to see the cost.
How Much Gravel: the Formula
area = length × width (or π × diameter² ÷ 4)
volume = area × depth × (1 + waste %)
weight = volume × bulk densityEverything is converted to metres first. A depth of 3 inches is a quarter of a foot, not 0.3 of one, which is the most common mistake in gravel orders done by hand.
Step-by-Step Example
A driveway surface 20 by 10 feet, 3 inches of crushed stone, at 40 per ton.
Area: 20 × 10 = 200 ft² (18.58 m²)
Depth: 3 in = 0.25 ft (0.076 m)
Volume: 200 × 0.25 = 50 ft³ (1.42 m³)
With waste: 50 × 1.05 = 52.5 ft³ = 1.94 yd³
Weight: 1.49 m³ × 1.6 t/m³ = 2.38 t = 2.62 US tons
Cost: 2.62 × 40 = 104.88In metric, a path 6 by 3 metres with 50 mm of pea gravel is 0.90 m³, or 0.95 m³ with 5% extra — about 1.42 tonnes, which is two 850 kg bulk bags.
Choosing the Depth
| Use | Typical depth |
|---|---|
| Paths, borders, decorative areas | 2 in / 50 mm |
| Gravel driveway surface | 3–4 in / 75–100 mm |
| Compacted sub-base under a drive or patio | 4–6 in / 100–150 mm |
Two inches is enough to hide a weed membrane and still be comfortable to walk on. Much deeper loose gravel feels like walking on a beach and lets car wheels dig ruts. A driveway gets its strength from the compacted sub-base, not from a thick layer of loose stone on top.
Gravel Weight per Cubic Yard and Cubic Metre
| Material | t/m³ | US tons per yd³ |
|---|---|---|
| Pea gravel | about 1.5 | about 1.26 |
| Crushed stone | about 1.6 | about 1.35 |
| Compacted sub-base | about 2.0 | about 1.69 |
These are typical loose or in-place figures. Wet stone is heavier, and stone size and shape change how tightly it packs, so if your supplier quotes their own density, use theirs. A compacted sub-base is heavier per volume because the roller squeezes out the air, so the same trench takes more tonnes of it.
Bags, Bulk Bags or a Loose Load
Bagged gravel is handy for a small border, but it is by far the most expensive way to buy stone. A 0.5 cubic foot bag is roughly 50 pounds; a small driveway needs a hundred of them.
For anything more than about a ton or a tonne, a bulk bag (often around 850 kg in the UK and Europe) or a loose tipper load is much cheaper. Check that the lorry can reach the drop point, and put a tarpaulin down if the load will be tipped onto a lawn or a driveway you want to keep clean.
Understanding Your Result
Gravel needed is the headline weight in US tons or metric tonnes.
Weight repeats it with pounds or kilograms.
Volume gives cubic yards and cubic feet, or cubic metres and litres, including the waste allowance.
Area and depth confirms the numbers the calculation used.
Bags converts the order to bags, and bulk bags in metric.
Cost multiplies the weight by your price, if entered.
Worth knowing gives the usual depths, or warns when a layer is too thin.
When Should You Use This Calculator?
Laying a gravel path or border and working out how many bags to buy.
Planning a gravel driveway, with the surface layer and sub-base worked out separately.
Comparing pea gravel with crushed stone, which weigh different amounts.
Checking a quote from a landscaper or supplier.
Filling a French drain or soakaway — measure it as a rectangle with its depth.
Common Mistakes
Reading 3 inches as 0.3 feet. It is 0.25 feet, and the error adds 20%.
Forgetting the sub-base. A driveway needs 4–6 inches of compacted base under the gravel you see.
Using one density for every stone. A compacted sub-base weighs about a third more per cubic yard than loose pea gravel.
Spreading it too thin. Under 2 inches, the membrane shows through within weeks.
Buying bags for a big job. Above about a ton, bulk delivery saves a lot.