Mulch & Soil Calculator
Work out how much mulch, compost or topsoil a bed needs — volume, bags, weight and cost, in imperial or metric.
Enter the bed size and depth — the volume, bag count and cost update as you type.
- Cubic yards
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- Cubic feet
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- Bags needed
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- Bed area
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- Approx. weight
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- Cost — by the bag
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- Cost — in bulk
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How it works
Mulch and soil are sold by volume, and volume is just area × depth. In imperial units the
calculator uses the standard landscaping formula
cubic yards = square feet × depth in inches ÷ 324 — 324 is 27 cubic feet per cubic
yard times 12 inches per foot. In metric it uses
cubic metres = square metres × depth in cm ÷ 100, and one cubic metre is 1,000
litres. A 20 ft × 10 ft bed at 3 inches deep is 200 sq ft × 3 ÷ 324 = 1.85 cubic yards, or 50
cubic feet — 25 of the standard 2 cu ft bags.
Pick a rectangle, a circle (area = π × radius²) or type the area straight in if you have already measured it. Bag counts are always rounded up to a whole bag, because half a bag is not a thing you can buy. The weight estimate multiplies the volume by a typical bulk density for the material you chose — roughly 400 kg/m³ for shredded bark, 1,200 kg/m³ for screened topsoil and 1,700 kg/m³ for pea gravel — which is what tells you whether a load fits in your car or needs a delivery. Everything is worked out in your browser with plain JavaScript: nothing is uploaded, there is no sign-up and there are no ads.
How deep? Rule of thumb: 2–3 inches (5–7.5 cm) to top up an established bed, 3–4 inches (7.5–10 cm) for a new bed or to suppress weeds. Keep mulch pulled back a few inches from tree trunks and stems. Costs are shown in whatever currency you type — the calculator never converts money — and the weights come from typical bulk densities that vary a lot with moisture, so treat them as a delivery sanity check rather than a guarantee.
Frequently asked questions
How much mulch do I need?
Multiply the bed area in square feet by the depth in inches and divide by 324 — that is your answer in cubic yards. A 20 ft × 10 ft bed at 3 inches deep is 200 × 3 ÷ 324 = 1.85 cubic yards, which is 50 cubic feet or 25 of the standard 2 cu ft bags. In metric the same sum is square metres × depth in cm ÷ 100 = cubic metres, so 24 m² at 7.5 cm is 1.8 m³, or 1,800 litres.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it takes 13.5 standard 2 cu ft bags, 18 bags of 1.5 cu ft, or 9 bags of 3 cu ft. Bulk delivery usually works out cheaper once you pass roughly two cubic yards, which is about 27 bags. This calculator shows the bag count next to both the bag price and the bulk price so you can see where that crossover falls for your supplier.
How deep should mulch be?
Two to three inches (5–7.5 cm) is enough to top up an established bed, and three to four inches (7.5–10 cm) is the usual depth for a new bed or for suppressing weeds. Going much deeper than four inches can starve roots of air and water. Keep mulch pulled back a few inches from tree trunks and plant stems rather than piling it against them.