Mulch calculator
How many bags or cubic yards of mulch a garden bed needs.
About this calculator
How much mulch do I need? This mulch calculator works out the volume for a rectangular or round bed from its size and the depth you want.
It gives cubic yards or cubic metres and the number of bags to buy, and checks that the depth suits most plants.
How it works
Volume is the bed’s area × the depth. A cubic yard is 27 cubic feet, so it covers about 108 square feet at 3 inches deep. The number of bags is the volume ÷ the bag size, rounded up.
Last reviewed:
Worked example
- Measure in: Feet and inches
- Bed shape: Rectangle
- Length: 20 ft
- Width: 4 ft
- Depth: 3 in
- Bag size: 2 ft³
Bags needed: 10 (0.74 yd³)
Common questions
How much mulch do I need?
For 100 square feet at 3 inches deep, about 0.93 cubic yards, or 13 bags of 2 cubic feet.
How deep should mulch be?
About 5 to 10 cm (2 to 4 in) for most beds. Keep it a little away from stems and tree trunks.
How many bags of mulch make a yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet, or 9 bags of 3 cubic feet.
Sources and further reading
The story behind it
Where the idea came from: The word mulch is thought to come from the Middle English molsh, meaning soft or rotting.
Mulch keeps soil moist, cooler in summer and free of many weeds. As organic mulches such as bark break down they feed the soil, which is why they need topping up every year or two.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
Meet the founder