Square Feet to Cubic Yards: Ordering Mulch, Gravel and Topsoil
Mulch, gravel, sand and topsoil are all ordered by volume, yet the area you want to cover is measured in square feet or square metres. The missing ingredient is depth. Multiply area by depth and you have volume; the only awkward part is converting inches to feet and cubic feet to cubic yards.
The shortcut below does the conversion in one step, and a coverage table lets you check the answer by eye. The same maths works for any loose material that you spread to a given thickness.
The one-step formula
A cubic yard is 27 cubic feet, and a depth in inches must be divided by 12 to become feet. Combine the two and the constants collapse into one number: 12 × 27 = 324.
cubic yards = area (ft²) × depth (in) ÷ 324For metric: cubic metres = area (m²) × depth (mm) ÷ 1,000.
Worked example: a garden bed of 200 ft² covered with 3 in of mulch. Volume = 200 × 3 ÷ 324 = 1.85 yd³. In cubic feet that is 1.85 × 27 = 50 ft³. If the bags are labelled 2 ft³, you need 50 ÷ 2 = 25 bags.
The same formula works for round areas once you have the area. A circle around a tree trunk, 6 ft across, has a radius of 3 ft and an area of 3.1416 × 3² = 28.3 ft². With 3 in of mulch, that is 28.3 × 3 ÷ 324 = 0.26 yd³, or 7.1 ft³. Bags of 2 ft³ give 3.5, so buy 4 bags.
Metric example: a 15 m² path with 75 mm of gravel needs 15 × 75 ÷ 1,000 = 1.125 m³. The mulch calculator, gravel calculator and topsoil calculator apply these steps and let you pick your units.
How far does a cubic yard go?
Turn the formula around and one cubic yard covers 324 ÷ depth square feet. This gives a fast reference:
| Depth | Area covered by 1 yd³ |
|---|---|
| 1 in | 324 ft² |
| 2 in | 162 ft² |
| 3 in | 108 ft² |
| 4 in | 81 ft² |
| 6 in | 54 ft² |
A common recommendation for mulch around plants is 2 to 3 inches, so one cubic yard covers about 108 to 162 ft². Gravel for paths and driveways, and topsoil for lawns or raised beds, are laid at different depths depending on the purpose and the product, so follow the maker's or supplier's advice for the depth itself.
When material is sold by weight
Gravel, sand and crushed stone are often sold by the ton or tonne, not the cubic yard. Converting needs a bulk density, the weight of one cubic yard of that particular material, and this varies with the type of stone, the particle size and how wet it is.
weight = volume × bulk density
As an illustration only, if a supplier says their gravel weighs 1.4 tons per cubic yard, then 2 yd³ weighs 2 × 1.4 = 2.8 tons. A US ton is 2,000 lb, a metric tonne is 1,000 kg and a UK ton is 2,240 lb, so confirm which one the price refers to. Ask the supplier for the density of the exact product you are buying, and calculate the volume from your own measurements.
Settling, compaction and extra
Loose material settles after spreading, and organic mulch breaks down over time. Gravel for a driveway or base layer is compacted, so the loose volume you order is larger than the finished volume. A planning allowance of 5% to 10% is common for garden jobs, and more may be sensible when the ground is uneven or the material is compacted.
For the 200 ft² bed above, 1.85 yd³ plus 10% is 2.04 yd³. Suppliers set their own minimum load and ordering increments, so ask what they offer; rounding up to 2 yd³ would be close to right here.
- Measure the depth you want after settling, not the depth when freshly spread.
- Subtract areas such as trees, stones and structures, but only if they are large.
- Split large or irregular areas into rectangles and circles, then add the volumes.
- Check how you will move and store the material: a bulk delivery needs a place to tip it.
If a supplier uses cubic metres and your tape measure uses inches, the volume converter turns one into the other without hand arithmetic.
- Mulch Calculator: Measure the bed, choose how deep the mulch should be, and the calculator shows the volume you need. Tell it the bag size and it counts the bags and prices them against a bulk delivery.
- Gravel Calculator: Measure the area you want to cover and the depth of the layer, and the calculator returns the volume of gravel, how much it weighs and, with a price per ton, what it will cost.
- Topsoil Calculator: Enter the width, length and depth of the area to see how much topsoil it takes in cubic yards or cubic metres, roughly what it weighs and, once you add a bag size and a price, how many bags to buy and what they cost.
This article is general information, not professional advice. See our Disclaimer and Editorial Policy.
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