About the mulch calculator
Mulch keeps soil moist, suppresses weeds, and gives beds a finished look. Too little and it won't do its job; too much and you risk smothering roots and wasting money. The right amount comes down to two things: the area of your beds and the depth you spread.
Enter the bed dimensions and your target depth. The calculator returns the volume in every common unit and the number of bags for the size you're buying.
How to use this calculator
- Measure each bed's length and width. Add separate beds together or calculate them one at a time.
- Choose a mulch depth. Two to three inches is typical for most beds.
- Pick your bag size — 2 cu ft is the most common size in US stores.
- Set a small allowance for curves and uneven edges, then read your results.
Worked examples
- A border 20 ft long and 3 ft wide, mulched 3 in deep.
- 20 × 3 × 3 ÷ 12 = 15 cu ft
- 15 ÷ 27 = 0.56 cu yd
- 15 ÷ 2 = 7.5
8 bags of 2 cu ft, before any allowance.
- Total bed area 400 sq ft at 2 in deep.
- 400 × 2 ÷ 12 = 66.7 cu ft
- 66.7 ÷ 27 = 2.47 cu yd
About 2.5 cu yd in bulk — a good point to compare bulk pricing against roughly 34 bags.
Measurement guidance
Recommended depths
Fine mulch and new beds: 2 inches (5 cm). Most bark and wood chip mulch: 2–3 inches (5–7.5 cm). Heavy weed pressure or coarse chips: up to 4 inches (10 cm). Refreshing an existing layer: often 1 inch is enough.
Keep mulch off stems
Leave a few inches of bare space around tree trunks and plant stems. Mulch piled against bark can hold moisture against it and invite rot and pests.
Tree rings
For a round ring, measure the diameter, square it, and multiply by 0.785 to get the area. Enter that area as length with a width of 1 to use the calculator.
Frequently asked questions
How many bags of mulch are in a yard?
One cubic yard equals 27 cubic feet, which is 13.5 bags of 2 cu ft — so 14 bags in practice.
How much area does a bag of mulch cover?
A 2 cu ft bag covers about 12 sq ft at 2 inches deep, or 8 sq ft at 3 inches deep.
Should I remove old mulch first?
Not usually. If the old layer is still a couple of inches thick, fluff it and add an inch of fresh mulch. If it has matted or built up past about 4 inches, remove some before adding more.
Is bulk mulch cheaper than bags?
Often, once you need more than a cubic yard or two. Delivery fees vary, so compare the total delivered price with the cost of the equivalent number of bags.