Gravel Calculator
Find how much gravel you need, by volume and by weight, and how many bags to buy. Enter each area's shape, size, and depth, and choose the type of gravel. For mulch or bark, use the Mulch Calculator. For sand, use the Sand Calculator. For a compacted base such as crusher run, use the Road Base Calculator.
Add more areas, or subtract areas that need no gravel, such as a patio.
- Choose US or Metric. This also sets the units of the results and the bag sizes: 0.5 cu ft bags for US, and 1 tonne and 800 kg bulk bags and 25 and 20 kg bags for Metric.
- Pick the shape of the area and enter its dimensions and Depth. For a shape that is not listed, choose Known area and enter the area directly.
- Use Add section for each extra area. Set a section to Subtract for parts that do not need gravel, such as a patio or a planting bed inside a gravel area.
- Choose the Gravel type. The Density field shows a typical density for that type. If your supplier gives a density, enter it in any of the units listed. The reset link under the field brings back the typical value.
- Keep the 10% waste allowance or change it. If you change it, Reset to 10% brings it back.
- If your bag is not listed, enter the volume or weight printed on the bag in Custom bag size to add it to the results.
- Optionally, enter a price per US ton, tonne, cubic yard, cubic foot, cubic meter, or bag to estimate the cost.
The dimension and depth fields accept whole numbers, decimals, fractions,
and mixed numbers, such as 12, 10.5,
3/4, or 2 1/2. Choose ft + in
as the unit to enter a length such as 12 ft 6 in in two fields.
How much gravel you need
The volume of a layer of gravel of even depth is:
Volume = area × depth
Convert every dimension to the same unit before you multiply. With dimensions in feet, divide cubic feet by 27 to get cubic yards. The waste allowance is added after subtracting any sections: total = net volume × (1 + waste % ÷ 100).
Gravel is often sold by weight, which is:
Weight = total volume × density
The density is the loose bulk density: the weight of a volume of gravel as it is delivered and spread, including the air between the stones. The calculator uses these typical values:
| Gravel type | Density |
|---|---|
| Crushed stone | 96 lb/ft³, 1.296 US tons/yd³, 1.538 t/m³ |
| Pea gravel or river rock | 98 lb/ft³, 1.323 US tons/yd³, 1.57 t/m³ |
These are the estimates for coarse aggregates in the Aggregate Tonnage Estimator of Vulcan Materials, a major US producer of crushed stone. The value for crushed stone also matches the loose unit weight of No. 57 stone, 95.4 lb/ft³, measured in a US Federal Highway Administration study (FHWA-HRT-15-034). Depending on the rock, coarse aggregates range from about 90 to 102 lb/ft³, so use your supplier's figure if you have one.
The number of bags is:
Bags = total volume ÷ volume per bag, or total weight ÷ weight per bag, rounded up
Bags are counted the way they are labeled. In the US, bags of gravel are labeled 0.5 cu ft, while their weight varies from 45 to 50 lb between brands, so they are counted by volume. The UK and Australian bags listed below are labeled by weight only, so they are counted by weight. The calculator shows these bag sizes:
| Bag | Examples |
|---|---|
| 0.5 ft³ | Pea gravel from Pavestone, Vigoro, and EarthEssentials by Quikrete |
| 1 tonne bulk | Bunnings (Australia) |
| 800 kg bulk | Travis Perkins and Wickes (UK) |
| 25 kg | B&Q (UK) |
| 20 kg | Travis Perkins and B&Q (UK) |
The calculator counts an 800 kg bulk bag as 800 kg, the weight the sellers state. The actual weight varies by a few percent, and wet gravel can make a bag heavier, up to about 850 kg.
The 10% waste allowance covers gravel settling as it is walked and rained on. In the same FHWA study, No. 57 stone lost about 12% of its volume from loosely placed to fully compacted by vibration. The calculator assumes spread gravel settles less than that, and uses 10%.
Types of gravel
Crushed stone, such as #57 or 20 mm stone, is angular and locks together as it settles, so it suits driveways, paths, and drainage. Pea gravel or river rock is small, rounded stone for walkways, play areas, and decorative beds. Rounded stones shift underfoot, so use edging to keep them in place.
Examples
A path or patio in feet
A 10 ft × 10 ft area, 4 in deep, is 33.33 ft³. With a 10% waste allowance, the total is 36.67 ft³, or 1.36 yd³ (1.04 m³). Of crushed stone at 96 lb/ft³, that weighs 1.76 US tons (3,520 lb). In 0.5 cu ft bags, that is 74 bags (36.67 ÷ 0.5 = 73.33, rounded up). At $45 per US ton, the cost is $79.20.
Metric dimensions
A 5 m × 4 m area, 5 cm deep, is 1 m³. With 10% added, the total is 1.10 m³. Of crushed stone at 1.538 t/m³, that weighs 1.69 tonnes (1,692 kg). That is 2 bulk bags of 1 tonne, 3 bulk bags of 800 kg, 68 bags of 25 kg, or 85 bags of 20 kg. At £30 per tonne, the cost is £50.75.
FAQ
About 1.3 US tons for crushed stone at 96 lb/ft³: a cubic yard is 27 ft³, and 27 × 96 = 2,592 lb. A cubic meter of the same stone weighs about 1.54 tonnes. Wet or denser stone weighs more.
A US ton of crushed stone at 96 lb/ft³ is about 20.8 ft³, which covers about 125 ft² at 2 in deep, or 83 ft² at 3 in deep. A tonne is about 0.65 m³, which covers about 13 m² at 5 cm deep.
A cubic yard is 27 ft³, so it takes 54 bags of 0.5 cu ft. For bags sold by weight, multiply the volume by the density to get the weight first: a cubic meter of crushed stone is about 62 bags of 25 kg.
About 1.36 yd³ (36.67 ft³) for a 10 ft × 10 ft area 4 in deep, with a 10% waste allowance. At 98 lb/ft³, that's about 1.8 US tons (3,593 lb), or 74 bags of 0.5 cu ft. For a different depth, enter it in the calculator.
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