How Much Gravel Do I Need? Cubic Yards, Tons and Bags Explained

By the SAA Tool editor, an IT support engineer · Last reviewed 9 October 2026 · 7 min read

Most gravel orders go wrong in one of two ways: a depth typed in the wrong unit, or a weight worked out with the wrong figure for the stone. This guide shows the maths in feet and in metres, where each number comes from, and examples you can check on a calculator. It's general information for planning: structural work and building rules need a qualified professional or an official source.

Step 1: area × depth, in one unit

Volume is length × width × depth, with all three in the same unit. Depths are usually given in inches or centimetres, so convert them first: divide inches by 12 (3 in is 0.25 ft, 4 in is 0.333 ft) and centimetres by 100 (7.5 cm is 0.075 m).

Then convert the volume. These factors are exact, from NIST Handbook 44:

• 1 cubic yard = 27 cubic feet (3 × 3 × 3), so divide cubic feet by 27.
• 1 cubic yard = 0.764554857984 m³, so 1 m³ is about 1.308 cubic yards.
• 1 cubic foot = 0.028316846592 m³.

Step 2: volume × density = weight

Many suppliers price bulk gravel by weight. The Engineering ToolBox gives dry gravel as 1,680 kg/m³, or 105 lb per cubic foot (104.9 if you convert exactly). That's about 2,830 lb, or 1.42 US tons, per cubic yard. It's the default in our Gravel Calculator, but real stone varies:

• Water. The same table lists wet gravel at 2,000 kg/m³, about 19% heavier. Buy wet stone by weight and you pay for the water: a tonne fills 0.595 m³ at the dry figure but only 0.5 m³ at the wet one.
• Air gaps. Solid limestone is 2,560 kg/m³ in the same table; a heap of gravel weighs less because much of it is air. Single-size stone such as pea gravel leaves gaps, while crushed stone with sand and fines fills them and weighs more.
• Packing. If 12 in of loose fill settles to 9 in, the same stone fills three quarters of the space, so it weighs a third more per cubic foot.

So ask your supplier what their stone weighs per cubic yard or per m³, whether that's loose or compacted, and which ton they mean. A US ton is 2,000 lb (907.18474 kg), a UK long ton is 2,240 lb and a tonne is 1,000 kg (see our metric and imperial guide).

Worked examples in both units

The Gravel Calculator gives the same figures, with bags rounded up.

Round and odd-shaped areas

• Circle: area = π × diameter² ÷ 4. A circle 8 ft across is 50.27 sq ft, so at 3 in deep it takes 12.57 cu ft (0.47 cu yd). A circle 2.5 m across is 4.91 m², so at 7.5 cm it takes 0.37 m³.
• Ring round a tree or pond: work out the outer circle and subtract the inner one. An 8 ft ring with a 2 ft clear centre, 3 in deep, is 12.57 cu ft minus 0.79 cu ft, or 11.78 cu ft.
• Triangle: base × height ÷ 2.
• Irregular plots: split them into rectangles and add the results. For a curving path, measure the width at several points, average the widths and multiply by the length along the middle.

If a plan gives the area in square yards, acres or hectares, the Area Converter switches it to square feet or square metres.

How deep should it be?

There's no single right depth. It depends on the job, the stone and what's underneath. Some published figures:

• Play areas. The US Consumer Product Safety Commission's Outdoor Home Playground Safety Handbook asks for at least 9 in (23 cm) of pea gravel or sand under equipment up to 5 ft (1.5 m) high, extending at least 6 ft (1.83 m) from it in every direction. It adds that an initial fill of 12 in (30 cm) compresses to about 9 in over time. Other countries have their own playground standards, so check yours.
• Driveways. These are built in compacted layers. UK government guidance on permeable front gardens describes about 150 mm (6 in) of compacted sub-base within roughly 200 to 250 mm (8 to 10 in) of construction. Our driveway layers guide compares this with US examples.
• Paths, borders, patios and drainage. No official figure suits every garden, as it depends on the stone, the base and the foot traffic. Ask your supplier, or a local extension service or gardening advisory body.

A climbing frame 6 ft square needs surfacing over 18 × 18 ft: at a 12 in fill that's 12 cu yd (9.17 m³), about 17 US tons of dry gravel. In metric, 5.5 × 5.5 m at 30 cm is 9.08 m³, about 15.25 tonnes.

How much extra to add

Order extra for two separate reasons:

• Waste and uneven ground: hollows, stone pressed into soft soil and spillage. The calculator adds 5% by default.
• Settling and compaction: gravel that's walked or driven on packs down. The playground handbook's 12 in to 9 in is a 25% drop, and a US gravel roads manual says ordinary compaction from traffic and rainfall makes most gravels shrink by at least 20%.

Watch the maths. If gravel shrinks by 25%, you need 1 ÷ 0.75 = 1.33 times the finished volume: 33% extra, not 25%. A 20% shrink needs 1 ÷ 0.8 = 1.25, or 25% extra. For a play area, simply enter the initial fill depth (12 in, not 9 in). For a driveway, use the Driveway Gravel Calculator, which adds 25% for compaction by default.

Bags or bulk?

Bags are labelled by volume (cubic feet or litres) or by weight (pounds or kilograms), so read the label. Quikrete's All-Purpose Gravel, for example, comes in 50 lb bags. To turn weight into volume, divide by the density: 50 lb ÷ 105 lb per cu ft is about 0.48 cu ft, so a cubic yard (about 2,830 lb) is about 57 of those bags. A cubic yard fills exactly 54 bags of 0.5 cu ft.

Bags suit small jobs, top-ups and spots a lorry can't reach. For bigger jobs, compare the price per ton or per cubic metre of bags against a bulk load, delivery included. The calculator suggests thinking about bulk once a job passes 40 bags; the 12 × 16 ft example needs 101.

Using the Gravel Calculator

1. Open the Gravel Calculator and choose Units: Imperial (feet, inches) or Metric (metres, centimetres). Your device remembers the choice.
2. Choose the Shape (Rectangle or square, or Circle), then enter the Length and Width, or the Diameter.
3. Enter the Depth in inches or centimetres. Don't convert it yourself.
4. Pick the Extra for waste and the Material: dry gravel, crushed stone or pea gravel; wet gravel; dry sand; or My supplier’s figure, which opens a box for tons per cubic yard or tonnes per m³.
5. Choose the Bags size: 0.5, 0.75 or 1 cu ft in imperial, 20 or 25 kg in metric.
6. Press Calculate (results also update as you type). You get the volume in three units and the weight, then a Details table with the material weight used, the amount with extra and the bag count. Reset restores the defaults.

It all runs in your browser. Imperial weights are in US tons, so for bags sold in pounds, multiply the tons with extra by 2,000 and divide by the bag weight. If a bag is marked in litres, the Volume Converter turns litres into cubic feet or cubic metres.

Common mistakes

• Depth in the wrong unit. Typing 3 in as 0.3 ft orders 20% too much; typing 7.5 cm as 0.75 m orders ten times too much.
• Dividing by 9 instead of 27. Nine converts square feet to square yards. 48 cu ft ÷ 9 = 5.33, three times the real 1.78 cu yd.
• Mixing up tons and tonnes. 10 US tons is 9.07 tonnes, and 10 tonnes is 11.02 US tons.
• Using a generic weight when you buy by weight. Ask for the figure for the stone you're actually buying.

Spotted a mistake or something out of date? Tell us and we'll fix it.