Mulch Calculator
Mulch volume = length × width × depth. A 40 × 8 ft bed at 3 in deep is 80 ft³ = 2.96 yd³, or 3.12 yd³ with 5% waste. The calculator gives yd³ and ft³; for bags, divide the ft³ by the bag size — 40 bags of 2 ft³. For stone, use the Landscape Rock Calculator.
How it's calculated: Volume = length × width × depth, plus waste; yd³ = ft³ ÷ 27; weight = volume × an assumed bulk density. Bags are a manual step: ft³ ÷ bag size (÷ 2 for 2 ft³ bags).
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Volume = Length × Width × Depth
Weight = Volume × bulk density
Run the calculation to see each step with your own numbers.
A 40 ft × 8 ft bed, 3 in of mulch, 5% waste.
Volume = 80 ft³ = 2.96 yd³ exact → order 3.12 yd³ with 5% (rounded up)
Bags, worked by hand: 80 ft³ ÷ 2 ft³ per bag = 40 bags, or 42 with the 5% (84 ft³) — or a 3-yard bulk delivery
- Rectangular bed of uniform depth.
- Bulk-mulch density varies enormously with type and moisture (400–1000 lb/yd³) — the weight is a rough guide only; order by volume.
- Bagged mulch is commonly 2 ft³ per bag — 1 yd³ ≈ 13.5 bags.
- How many bags in a cubic yard?
- About 13.5 bags of the common 2 ft³ size (27 ft³ ÷ 2). Bulk delivery is usually cheaper above ~2 yd³ once you factor in handling.
- Why is the weight so uncertain?
- Fresh, wet hardwood mulch can weigh twice what dry pine-bark mulch does. Order mulch by volume, not weight.
- How much mulch does a 10 × 10 ft bed need?
- About 0.93 yd³ (25 ft³) for its 100 ft² at 3 in deep, or 0.98 yd³ with 5% waste. The calculator stops at volume; divide the 25 ft³ by your bag size for bags — 12.5 bags of 2 ft³, or 14 with the waste allowance.
- How many square feet does a cubic yard of mulch cover?
- About 108 ft² at 3 in deep, 162 ft² at 2 in and 81 ft² at 4 in — divide 27 ft³ by the depth in feet. Add a little for settling and uneven spreading.
Volume
Standard geometry: Volume = L × W × D. Unit conversions per NIST SP 811.
Bulk density
Bulk wood/bark mulch ≈ 400–550 kg/m³ green (≈700–1000 lb/yd³). Composting Council / landscape-supply figures. Very moisture-dependent.
About the Mulch Calculator
The Mulch Calculator converts a bed area and depth into cubic yards (and cubic feet) of mulch. It does not count bags itself: divide the cubic feet by the bag size on the label to get a bag count. Mulch weight varies enormously with type and moisture, so order by volume, not weight. Use 2–3 inches on an established bed and 3–4 on a new one; bulk delivery usually beats bags above about two cubic yards.
What you enter
- Length
- Width
- Depth — 2–3 in for an established bed; 3–4 in for a new bed or heavy weed pressure.
- Waste allowance — Default 5%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Mulch volume — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Approx. weight — Suppliers usually sell by weight. Weight uses the material's bulk density (adjustable).
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Landscape Rock Calculator — Decorative rock by volume and weight for a landscaped bed.
- Cubic Yard Calculator — Convert a length, width and depth into cubic yards, cubic feet or cubic metres.
- Gravel Calculator — Gravel by volume and by delivered weight for driveways, paths and fill.
- Topsoil Calculator — Topsoil by volume and by delivered weight for a lawn, bed or fill area from its area and depth.
Part of the Landscaping & Driveway calculators.