Gravel, Mulch & Topsoil Calculator
Find out how much gravel, mulch, sand or topsoil to order for a bed, path or base, in cubic yards, tons, cubic metres or bags.
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Gravel, mulch, sand and topsoil calculator
Results appear here as you type.
How the calculator works
Gravel, mulch, sand and topsoil are all sold by volume (cubic yards, cubic metres or bags) or by weight (tons or tonnes). This calculator works out the volume first, from area × depth, and then converts it into the units suppliers use: cubic yards or m³, the number of bags of the size you type in, and an approximate weight for quarry products sold by the ton.
Weight is the less certain number. The same cubic yard of gravel weighs more when it’s wet, and a fine, well-graded stone packs denser than a coarse, single-size one. The densities below are typical planning values, not measurements of your supplier’s product, so check the weight with your quarry if you’re ordering by the ton. Vulcan Materials’ tonnage estimator is one example of a supplier tool that uses product-specific weights.
The formulas
Volume (ft³) = area (ft²) × depth (in) ÷ 12 Cubic yards = area (ft²) × depth (in) ÷ 324 Volume (m³) = area (m²) × depth (mm) ÷ 1000 Weight = volume × density Bags = volume ÷ bag size (round up) Circle area = π × diameter² ÷ 4
The 324 comes from 12 inches per foot × 27 cubic feet per yard. It gives a handy coverage rule: one cubic yard spreads over 324 ft² at 1 in deep, 162 ft² at 2 in, 108 ft² at 3 in and 81 ft² at 4 in. In metric, one cubic metre covers 20 m² at 50 mm, 13.3 m² at 75 mm and 10 m² at 100 mm.
Typical densities used
| Material | US tons per yd³ | Tonnes per m³ | Notes |
|---|---|---|---|
| Gravel / crushed stone | 1.4 | 1.66 | Varies by stone and grading; often quoted around 1.3–1.5 |
| Sand (dry, loose) | 1.35 | 1.60 | Wet sand is heavier |
| Topsoil (dry) | 1.1 | 1.31 | Moisture and organic content change this a lot |
| Wood mulch | 0.3 | 0.36 | Usually bought by volume, so the weight is only a rough guide |
Worked examples
Mulching two flower beds
Two beds of 20 × 4 ft make 160 ft². At 3 in deep: 160 × 3 ÷ 324 = 1.48 yd³, or 40 ft³. In 2 ft³ bags that is 20 bags; one bulk yard plus a few bags would also do it. The University of Maryland Extension recommends keeping mulch shallow (1–3 in for bark mulch) and about 3 in away from tree trunks, so don’t go deeper than you need.
A gravel path 30 ft long and 3 ft wide
90 ft² at 3 in deep: 90 × 3 ÷ 324 = 0.83 yd³. At 1.4 tons per yard that’s about 1.17 tons. Gravel that will be compacted ends up thinner than it was spread, so ask your supplier how much extra to allow for the product you’re buying.
Filling a raised bed (metric)
A bed 2.4 m × 1.2 m filled 300 mm deep holds 2.4 × 1.2 × 0.3 = 0.864 m³ (864 litres). That is 18 bags of 50 L, or about 1.1 tonnes of topsoil at the typical density above. Bagged composts and soils often settle after watering, so many gardeners top up later rather than overfill on day one.
Buying tips
- Bulk vs bags. A cubic yard is 27 ft³, the same as 13.5 bags of 2 ft³ or 9 bags of 3 ft³. Compare the bulk price plus delivery with the bag price before you choose.
- Check delivery minimums. Many yards have a minimum load or a small-load fee, which can make a slightly bigger order the cheaper one.
- Measure depth after you level. Rake to the finished level and check depth in several spots before you order the last top-up.
- Before you dig for edging or a sub-base, find out where buried utilities are. In the US, contact 811 before you dig.
Frequently asked questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 ft³, so it equals 13.5 bags of 2 ft³ or 9 bags of 3 ft³. Round up to whole bags.
How much does a yard of gravel weigh?
A common planning figure is about 1.4 US tons per cubic yard (about 1.66 tonnes per m³), but it varies with stone type, grading and moisture. Ask your quarry for the weight of the specific product.
How deep should mulch be?
The University of Maryland Extension recommends keeping mulch shallow, generally 1–3 inches depending on the type, and keeping it about 3 inches away from tree trunks.
How much area does a cubic yard cover?
About 324 ft² at 1 in deep, 162 ft² at 2 in, 108 ft² at 3 in and 81 ft² at 4 in. In metric, 1 m³ covers 10 m² at 100 mm or 20 m² at 50 mm.
Should I add extra for compaction?
Usually, yes, for gravel and soil that will be compacted or will settle. The right amount depends on the material, so ask your supplier and enter it in the Extra field.