Topsoil and mulch calculator: cubic yards, bags and tons
This topsoil calculator and mulch calculator work out how much soil, mulch or compost you need for a lawn, garden bed, raised bed or tree ring. Enter the size of the area and the depth, and it returns cubic yards, cubic metres, cubic feet, the number of bags and the weight in tons or tonnes.
Use it as a topsoil calculator for a lawn (4 to 6 in for a new lawn), as a mulch calculator for bags (2 to 3 in on beds), or as a compost calculator. Choose a rectangle, a circle or a known area, feet or metres, and add a little extra for settling.
Bags are counted by volume because that is how bagged mulch and soil are sold. Everything is computed in your browser; supplier loads can differ, so treat the answer as an ordering estimate.
How to use the Topsoil & Mulch Calculator
- Pick feet and inches or metres and millimetres, then the material: topsoil, mulch, compost or your own density.
- Choose the area shape and enter its dimensions, or type the area if you have measured it.
- Enter the depth you want to spread.
- Add 10% for settling and uneven ground, choose a bag size, and optionally a price per cubic yard, m³, bag or ton.
- Read the cubic yards, bags and tons, and copy the summary for the garden centre or the landscape supplier.
Topsoil & Mulch Calculator features
Soil, mulch or compost
Presets for bulk density that you can edit for wet or dry material.
Bags or bulk
Bag sizes from 0.5 to 3 ft³ (14 to 85 L) and bulk cubic yards or m³.
Three area shapes
Rectangle, circle for tree rings and round beds, or a measured area.
Weight too
US tons and tonnes for delivery trucks that charge by weight.
Cost
Price per cubic yard, m³, bag, ton or tonne in six currencies.
How much topsoil or mulch do I need?
Volume = area × depth. In US units, cubic yards = square feet × depth in inches ÷ 324. A 20 × 10 ft bed is 200 ft². At 4 in deep that is 200 × 4 ÷ 324 = 2.47 cubic yards, or 66.7 ft³. In 2 ft³ bags that is 34 bags. Add 10% for settling and the order is 2.7 cubic yards.
The same bed mulched to 2 in needs 1.23 cubic yards (17 bags of 2 ft³). In metric, area (m²) × depth (m) gives cubic metres: 100 m² at 75 mm is 7.5 m³.
Weight uses a bulk density. Topsoil is taken as 950 kg/m³ (1,600 lb per cubic yard), the loose density in Caterpillar's earthwork tables, the same figure used by the gravel calculator; mulch about 400 kg/m³ and compost about 600 kg/m³ are typical values that vary with moisture and material. Edit the density if your supplier quotes another figure.
Typical depths and coverage
One cubic yard covers 324 ft² an inch deep. These depths are common gardening guidance, not rules, and plants differ.
| Job | Depth | Coverage of 1 cubic yard |
|---|---|---|
| Mulch on beds | 2 to 3 in (50 to 75 mm) | 108 to 162 ft² |
| Topdressing a lawn | 1/2 to 1 in (12 to 25 mm) | 324 to 648 ft² |
| Topsoil over a lawn before seeding | 4 to 6 in (100 to 150 mm) | 54 to 81 ft² |
| Raised bed | 8 to 12 in (200 to 300 mm) | 27 to 40 ft² |
Tips and limits
- Topsoil settles after watering. Order about 10% extra, or less for light mulch.
- Mulch against a tree trunk should stay a few inches clear of the bark, and deeper than 3 in can suffocate roots. Use a ring shape for a tree.
- For stone paths and drainage layers use the gravel calculator; for digging out first, the excavation calculator; for odd areas the area calculator.
- Soil quality, delivery fees and minimum load sizes are not included.
Topsoil & Mulch Calculator FAQ
How many cubic yards of topsoil do I need?
Multiply the area in square feet by the depth in inches and divide by 324. A 20 × 10 ft area at 4 in needs about 2.5 cubic yards.
How many bags of mulch do I need?
Find the volume in cubic feet and divide by the bag size. 200 ft² at 2 in is 33.3 ft³, or 17 bags of 2 ft³.
How deep should mulch be?
Usually 2 to 3 inches (50 to 75 mm) on beds. Too thick a layer can hold water against stems and block air to the roots.
How much does a cubic yard of topsoil weigh?
Loose topsoil is about 1,600 lb (0.8 US ton) per cubic yard by the Caterpillar table used here; wet soil can be much heavier. Use your supplier's figure when buying by weight.
How much topsoil do I need for a lawn?
For a new lawn, spread 4 to 6 inches over the area, so one cubic yard covers about 54 to 81 ft².
Is this a compost calculator too?
Yes. Pick compost, which sets a typical density of 600 kg/m³, or enter your own, and use the same area and depth.