Mulch Calculator
Free mulch calculator that turns a bed's length, width, and depth into cubic yards, cubic feet, and 2-cubic-foot bags. Enter your dimensions to see how much bulk or bagged mulch to order and what it should cost.
Calculate how much mulch you need
How the mulch calculator works
Spreading mulch is really a volume problem: you are covering a bed of a certain area to a certain depth. To calculate mulch, multiply the bed's length by its width to get square feet, multiply by the depth in feet, and you have cubic feet; divide by 27 for cubic yards. A 20 ft by 8 ft bed at 3 inches deep works out to (20 × 8 × 3 ÷ 12) ÷ 27 = 1.48 cubic yards, or about 40 cubic feet — roughly twenty 2-cubic-foot bags.
Bulk mulch is ordered by the cubic yard and bagged mulch by the cubic foot, which is why the same pile of material has two different unit prices. Knowing how much mulch you need in both units lets you compare a scoop delivery against a pallet of bags before you buy.
Depth, coverage, and rubber mulch
Depth drives everything. One cubic yard covers about 108 square feet at 3 inches, 162 square feet at 2 inches, and only 81 square feet at 4 inches, so doubling the depth halves the coverage. Most organic mulches — shredded hardwood, pine bark, cedar — are spread 2 to 4 inches deep and topped up each year as they break down.
Rubber mulch behaves differently: it does not decompose, so it is laid thinner, about 1.5 inches, and lasts for years. Set the depth field to 1.5 and this tool doubles as a rubber mulch calculator, giving cubic feet and bag counts for playground or landscape rubber. Keep mulch a couple of inches back from trunks and stems to avoid rot regardless of the material.
How to use this calculator
- Measure each bed in feet. Run a tape along the length and width of every bed and record both in feet. For a curved or kidney-shaped border, measure the widest points and treat it as a rectangle — mulch is forgiving, and a small over-order beats a second trip.
- Pick a spreading depth. Choose 2–3 inches to refresh color on an established bed and 3–4 inches over bare soil to hold moisture and block weeds. Shredded bark settles, so measure loose depth. This depth choice is the single biggest factor in how to calculate how much mulch you need.
- Convert the beds to cubic yards. The mulch calculator multiplies area by depth in feet and divides by 27, so several beds add up into one bulk order measured in mulch calculator yards — the unit a landscape-supply yard delivers by the scoop.
- Compare bags against bulk. The tool also counts 2-cubic-foot bags so you can compare a bagged run to a bulk delivery. Around 13.5 standard bags equal one cubic yard, and bulk usually wins once you pass roughly two or three yards.
Frequently asked questions
How to calculate how much mulch I need for a new bed?
Multiply the bed's length by its width to get square feet, multiply by the depth in feet (inches ÷ 12), and divide by 27 for cubic yards. A 20 × 8 ft bed at 3 inches needs about 1.5 cubic yards.
How many bags of mulch are in a cubic yard?
About 13.5 bags if each bag holds 2 cubic feet, because a cubic yard is 27 cubic feet. Larger 3-cubic-foot bags give you 9 per yard.
How deep should mulch be?
Two to three inches keeps an established bed looking fresh; three to four inches over bare soil suppresses weeds and holds moisture. Deeper than four inches can smother roots and stay soggy.
Does the rubber mulch calculator use a different depth?
Yes. Rubber mulch does not break down, so it is laid about 1.5 inches deep instead of 3. Set the depth field to 1.5 and the volume, bag, and cost results update for rubber.
Are 2026 mulch prices included?
The default of $40 per cubic yard reflects 2026 bulk-delivered pricing, which typically ranges from about $30 to $45 per yard. Bagged mulch costs more per cubic foot; always enter your own local quote.
Bed size vs cubic yards and bags
| Bed size | Depth | Cubic yards | 2 cu ft bags |
|---|---|---|---|
| 10 × 4 ft | 3 in | 0.37 yd³ | 5 bags |
| 20 × 8 ft | 3 in | 1.48 yd³ | 20 bags |
| 30 × 10 ft | 3 in | 2.78 yd³ | 38 bags |
| 40 × 12 ft | 4 in | 5.93 yd³ | 80 bags |
Once an order climbs past two or three cubic yards, bulk delivery is almost always cheaper per yard than bagged, and there is far less plastic to haul away.