Mulch Calculator
Mulch is shredded wood or bark spread over beds to hold moisture, block weeds and finish a yard. Work out how many cubic yards — or 2 cu ft bags — you need below.
Sets a typical depth — tweak anything below.
For a 20 ft × 10 ft area at 3 in deep, order about 2.04 cubic yards (0.52 US tons) of mulch.
Estimates only. Densities vary by moisture, compaction and supplier — confirm quantities before ordering.
What is mulch?
Mulch is shredded or chipped wood and bark spread as a top layer over soil. Common types are shredded hardwood, pine bark, cedar, and dyed mulch in black, brown or red. It's sold in bulk by the cubic yard or in bags that hold 2 cubic feet — not the 0.5 cu ft bags gravel comes in.
What is mulch used for?
It goes on garden beds, around trees and shrubs, along foundations, and on playgrounds. A layer holds moisture in the soil, smothers weeds, evens out soil temperature, and makes a bed look finished. Unlike gravel, mulch breaks down over a season or two and gets topped up rather than installed once.
How much does mulch weigh?
A cubic yard of mulch weighs about 0.25 US tons — roughly 300 kg/m³, or about 19 lb/ft³. Moisture and compaction shift this, so the calculator applies this density and lets you change it in the extra options if your supplier quotes a different figure.
Coverage by depth
| Depth | Coverage per cubic yard | Bags per 100 sq ft (2 cu ft each) |
|---|---|---|
| 1 inch | 324 sq ft | 4.2 bags |
| 2 inches | 162 sq ft | 8.3 bags |
| 3 inches | 108 sq ft | 12.5 bags |
| 4 inches | 81 sq ft | 16.7 bags |
A cubic yard is 27 cubic feet, so it holds 13.5 bags. 3 inches is the usual depth for beds.
Common mistakes to avoid
- Guessing the depth. Too shallow and the material shifts and shows the ground beneath. Most surface layers want 2–4 inches; load-bearing bases are built up thicker.
- Forgetting to convert inches to feet. Depth is quoted in inches but volume math is in feet — 4 inches is 0.33 ft, not 4. The calculator handles this, but hand estimates often don't.
- Skipping the waste allowance. Ground is never perfectly flat and material settles once it's placed. Order 5–10% extra so a small shortfall doesn't trigger a second delivery.
- Using the wrong density. Each material weighs differently, so tonnage can be off by 20%+ if you use a generic figure. Pick the right material and adjust the density if your supplier differs.
- Buying bags for a big job. Bagged material costs far more per cubic yard than bulk. Past roughly one cubic yard, a bulk delivery is almost always cheaper.
Frequently asked questions
How deep should mulch be?+
3 inches for beds — deep enough to block weeds, shallow enough to let water and air through. Going past 4 inches doesn't help and starts to suffocate roots. Around a tree, keep it 2–3 inches and pull it back a few inches from the trunk: piling it against the bark ('volcano mulching') traps moisture and rots the tree. Topping up an existing bed usually takes 1–2 inches, not a full 3.
How many bags of mulch are in a cubic yard?+
13.5 bags, since mulch bags hold 2 cubic feet and a cubic yard is 27 cubic feet. Round up to 14. This is the number that decides bulk vs bags: at roughly $4 a bag, a yard's worth of bags runs about $55 versus $30–$50 delivered in bulk — and that's 14 bags to haul and split open. Under about 6 bags, bagged is easier; over that, order bulk.
How much area does a yard of mulch cover?+
About 108 square feet at the recommended 3 inches deep, or 162 square feet at 2 inches. So a yard covers roughly a 10 × 10 bed at proper depth. Measure your beds, enter them above, and you'll get the yards and the bag count.
How much does a yard of mulch weigh?+
Roughly 500 lb a cubic yard dry — about a quarter of a ton, and a fraction of what gravel weighs (a yard of gravel is around 1.4 tons). But mulch soaks up water: after heavy rain the same yard can weigh double. That matters for hauling — a half-ton pickup handles 2–3 yards of dry mulch easily, where it can barely take one yard of gravel.
Should I put landscape fabric under mulch?+
For mulch, usually no — and this is the opposite of the answer for gravel. Mulch is meant to break down into the soil, and fabric blocks that while weed seeds just sprout in the decomposing mulch on top of it anyway. A year or two in, you're left with fabric that's fraying up through the bed and impossible to plant into. Use fabric under gravel, which doesn't decompose; for mulch, lay it thick enough (3 inches) and let it do the work itself.