Mulch Calculator
Find out how many cubic yards or bags of mulch you need for a garden bed.
How to use this mulch calculator
Measure the length and width of your bed in feet, choose how deep you want the mulch, and pick the bag size your store sells. The calculator gives you the volume in cubic feet and cubic yards, plus the number of bags rounded up so you don't come home short.
Use the Shape menu for round tree rings (measure straight across the middle for the diameter), triangular corner beds, or L-shaped beds that wrap around a corner. For anything more unusual, split it into simple shapes, work out each one, and add the results together.
How deep should mulch be?
| Use | Recommended depth |
|---|---|
| Refreshing an existing bed | 1–2 inches |
| New flower or shrub bed | 2–3 inches |
| Weed suppression | 3–4 inches |
| Paths and play areas (wood chips) | 4–6 inches |
More than about 4 inches in a planting bed can keep water and air from reaching the roots. Keep mulch a few inches away from tree trunks and plant stems so they don't rot.
The math behind it
Volume in cubic feet = length × width × (depth ÷ 12). Divide cubic feet by 27 to get cubic yards, which is how bulk mulch is sold. Divide cubic feet by the bag size to get the number of bags.
Example: a 20 × 4 ft bed at 3 inches deep is 20 × 4 × 0.25 = 20 cubic feet, or about 0.74 cubic yards. That's 10 bags of 2 cu ft mulch.
Bags or bulk?
Bags are easier for small jobs and don't need a truck. Once you need more than about 2 cubic yards (roughly 27 two-foot bags), bulk delivery from a landscape supplier is usually cheaper per yard. Ask about the delivery fee and minimum order before you compare.
Common mistakes
- Measuring in inches or yards but entering the number as feet.
- Forgetting that old mulch settles. Measure the depth you want to add, not the total depth.
- Not buying a little extra. Mulch compacts after watering, so 5–10% extra is a good cushion.
Often used together
Quick answers
How much area does a bag of mulch cover?
A 2 cubic foot bag covers about 8 square feet at 3 inches deep, or 12 square feet at 2 inches deep.
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 or 9 bags of 3 cu ft.
When is the best time to mulch?
Mid to late spring, once the soil has warmed up, is the most common time. A fall top-up also helps protect roots over winter.