How to use the mulch calculator
- Choose metric or imperial and the shape of your bed. For several beds, calculate each and add them up.
- Enter the depth of mulch you want once it's spread.
- Pick the bag size you plan to buy — the options change with the units.
The formula
volume = area × depth × (1 + extra %)
bags = volume ÷ bag size (rounded up)
Coverage of a 2 cu ft bag at different depths:
| Depth | Area covered by one 2 cu ft bag |
|---|---|
| 2 in | 12 sq ft |
| 3 in | 8 sq ft |
| 4 in | 6 sq ft |
Worked examples
Imperial: 100 sq ft of beds at 3 in deep = 25 ft³; plus 5% = 26.2 ft³ → 14 bags of 2 cu ft.
Metric: 10 m² at 5 cm deep = 0.5 m³ (500 L); plus 5% = 525 L → 8 bags of 70 litres.
Tips for buying mulch
- Check the bag label. Bags are sold by volume (cubic feet or litres). Use the number printed on the bag.
- Bulk for big jobs. If you need dozens of bags, compare the price of a bulk delivery — the calculator shows the cubic yards or cubic metres.
- Top-ups need less. If there's still some mulch on the bed, enter only the extra depth you're adding.
Common mistakes to avoid
- Forgetting the mulch already there. For a top-up, enter only the extra depth.
- Assuming every bag is the same size. Bags range from 1.5 to 3 cu ft or 50 to 100 litres — use the size on the label.
- Measuring a curved bed as a rectangle. It's safe but over-buys; use the circle shape or split the bed up.
Measuring an awkward shape? See how to measure an irregular area.
Frequently asked questions
How much does a 2 cubic foot bag of mulch cover?
About 12 sq ft at 2 inches deep, 8 sq ft at 3 inches, or 6 sq ft at 4 inches. That's simple geometry: 2 cubic feet divided by the depth in feet.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cu ft, 18 bags of 1.5 cu ft, or 9 bags of 3 cu ft. You can only buy whole bags, so round up.
How many litres of mulch do I need per square metre?
One square metre at 5 cm deep needs 50 litres (0.05 m³), and at 7.5 cm deep it needs 75 litres. Multiply by your area, or let the calculator do it and convert to bags.
Is bagged or bulk mulch cheaper?
For large areas, bulk mulch by the cubic yard or cubic metre is often cheaper per unit of volume, but it is delivered in one pile. Compare prices per cubic yard or per cubic metre — the calculator shows the bulk volume as well as the bag count.
Sources
Last updated 10 November 2026. Found a mistake? Tell us.