The short version
One cubic yard of mulch covers about 100 square feet at 3 inches deep. That's the only number most people need to memorize. Measure your bed, divide by 100, and round up.
The math
The exact formula is:
cubic yards = (square feet × inches deep) ÷ 324
The 324 comes from 12 inches per foot × 27 cubic feet per cubic yard. You'll see this same constant in every soil and mulch calculator on the internet.
Worked example. You've got two beds across the front of the house. One is 4 ft × 25 ft along the porch (100 sq ft). The other curves around the driveway and measures roughly 8 ft × 30 ft (240 sq ft). Total: 340 sq ft.
At 3 inches deep:
- 340 sq ft × 3 in ÷ 324 = 3.15 cubic yards
Round up to 3.5 yards (always round up — a half-yard short means a wasted trip), or order 4 yards if you're also planning to top-dress around the trees.
Bagged math: a 2 cu ft bag covers about 8 sq ft at 3". That same 340 sq ft project is 43 bags. Past 5 bags you're already cheaper buying bulk by the yard, and we load it for free.
Depth cheat sheet:
| Depth | One cu yd covers |
|---|---|
| 2" | 162 sq ft |
| 3" | 108 sq ft |
| 4" | 81 sq ft |
| 6" (playground fall zone, compacted to ~9") | 54 sq ft |
In DFW, 3 inches is the right depth for the average flower bed — enough to suppress weeds and hold soil moisture through a 100-degree July, not so much you suffocate roots or attract pillbugs. Pull mulch back 2 inches from tree trunks and plant stems. No volcano mulching.
Common mistakes
- Forgetting depth. A 200 sq ft bed at 2" is 1.25 yards; at 4" it's 2.5 yards. Same bed, double the order. Always measure depth too.
- Measuring on a hot, dry day and ordering "to the inch." Mulch settles 15-20% after the first heavy rain. Order to your finished depth, not the depth-on-day-one.
- Ignoring the existing layer. If you already have 2" of partially decomposed mulch from last year, you only need 1-1.5" of fresh material on top. Don't bury the bed under 6 inches of new mulch.
- Forgetting waste. Add 10% for spillage on the tarp, the dribble between wheelbarrow trips, and the spot you'll inevitably want to thicken up.
What to do next
Punch your beds into the mulch calculator — it does the sq-ft × depth ÷ 324 math, rounds to whole yards, and offers landscape fabric + edging on the way out. If you've got a mixed-bed project and want to be walked through it, the mulch-bed wizard asks 4 questions and builds the order for you. Ready to pull the trigger? Shop bulk mulch and bagged prices.
Also useful
- How much topsoil for a raised bed or yard — same cubic-yard math, different material
- How to measure sod for your lawn — if the front yard's getting the full treatment