Mulch Calculator
Measure your beds, choose a depth and see how many cubic yards or bags of mulch to buy. Add as many beds as you need, including round tree rings, and compare bagged with bulk.
How to use the mulch calculator
- Enter the first bed: rectangle, circle (for tree rings) or triangle (for corner beds).
- Click Add another area for each extra bed. The calculator adds them all up.
- Set the depth. 2–3 in suits most beds; don't go above 4 in.
- Check the bag size on the bags you plan to buy (most are 2 ft³). The result shows bags for 1.5, 2 and 3 ft³ too.
- Enter your bag price and your supplier's price per cubic yard under Cost estimate to see which is cheaper for your job.
How much mulch do I need?
Multiply the area of each bed by the depth, convert to cubic yards and add a little for settling and spills:
- Volume (ft³) = area (ft²) × depth (in) ÷ 12 × (1 + waste)
- Cubic yards = cubic feet ÷ 27
- Bags = cubic feet ÷ bag size, rounded up
A cubic yard is 27 ft³, so it fills 13.5 bags of 2 ft³, 18 bags of 1.5 ft³ or 9 bags of 3 ft³. Spread 1 in deep, one cubic yard covers 324 ft²; at 3 in it covers 108 ft².
Worked example: a 20 ft × 5 ft bed, 3 in deep
This is the bed loaded in the calculator above.
- Area: 20 × 5 = 100 ft².
- Volume: 100 × 3 ÷ 12 = 25 ft³. Add 5%: 26.25 ft³.
- Cubic yards: 26.25 ÷ 27 = 0.97 yd³.
- Bags: 26.25 ÷ 2 = 13.1, rounded up to 14 bags of 2 ft³. In 1.5 ft³ bags that is 18; in 3 ft³ bags, 9.
The weight shown (583 lb) is only a rough guide: suppliers quote anything from about 200 to 1,000 lb per yard depending on the wood and how wet it is.
How deep should mulch be?
Penn State Extension recommends a 2–4 in layer of organic mulch and no more, using less on poorly drained soil, because deeper layers can harm roots. Most flower and shrub beds look and work best at 2–3 in. If you are topping up last year's mulch, measure what is left and only add the difference; the calculator warns you above 4 in.
Mulch coverage by depth
| Depth | Area 1 yd³ covers | Yd³ per 100 ft² | 2 ft³ bags per 100 ft² | 3 ft³ bags per 100 ft² |
|---|---|---|---|---|
| 1 in | 324 ft² | 0.31 | 5 | 3 |
| 2 in | 162 ft² | 0.62 | 9 | 6 |
| 3 in | 108 ft² | 0.93 | 13 | 9 |
| 4 in | 81 ft² | 1.23 | 17 | 12 |
No waste added. One cubic yard is 27 ft³: 13.5 bags of 2 ft³ or 9 bags of 3 ft³.
Mulching tips
- Keep mulch off trunks and stems. Leave a few inches of bare soil around the base of trees and shrubs. Piling mulch against the bark ("volcano mulching") traps moisture against it.
- Measure tree rings as circles. Use the circle shape with the ring's full diameter. The bare patch you leave around the trunk is small, so the result errs slightly on the generous side.
- Bags vs bulk: bags are easy for a few small beds and keep mulch dry in the car. For a cubic yard or more, compare a bulk delivery quote with your bag total; enter both prices under Cost estimate.
- Measure odd shapes in pieces. Split a curved bed into a rectangle plus a circle or triangle and add each as a separate area.
Frequently asked questions
How many bags of mulch are in a yard?
A cubic yard is 27 ft³, so it equals 13.5 bags of 2 ft³ (buy 14), 18 bags of 1.5 ft³ or 9 bags of 3 ft³.
How much area does a yard of mulch cover?
About 162 ft² at 2 in deep, 108 ft² at 3 in and 81 ft² at 4 in. The general rule is 324 ft² divided by the depth in inches.
How many bags of mulch do I need for 100 square feet?
At 3 in deep, 100 ft² needs 25 ft³ of mulch: 13 bags of 2 ft³ (12.5 rounded up), or about 14 with a 5% allowance. At 2 in it is 9 bags.
How thick should mulch be?
2–3 in for most beds. Penn State Extension advises no more than 4 in of organic mulch, and less on poorly drained soil.
How much does a yard of mulch weigh?
It varies a lot. Landscape suppliers quote figures from around 200–500 lb (Hensons') to 600–1,000 lb (McCarty Mulch & Stone) per cubic yard, depending on the type of wood and its moisture.