Mulch Calculator — Cubic Yards & Bags
Enter your bed area and how deep you want the mulch, and get the volume in cubic yards plus the number of bags — with the formula and a worked example.
Calculator
Covering 300 sq ft at 3.0 in deep needs about 2.78 cu yd of mulch — roughly 38 bags of 2.0 cu ft. Bulk by the yard is usually cheaper than bags above ~2–3 cu yd. Buy about 5–10% extra and confirm the bag coverage.
Mulch does three jobs at once: it holds moisture in the soil, smothers weeds, and finishes a bed so it reads as cared-for. The only real question at the garden center is how much — and that is pure geometry. Mulch is spread as an even layer, so the volume is your bed area multiplied by the depth of the layer, converted to cubic yards. This tool does that conversion and then tells you how many bags that works out to, so you can decide between buying bags or ordering a bulk load by the yard.
Bagged mulch is convenient for small beds and easy to carry, but the price per cubic yard climbs fast. Above roughly two to three cubic yards, a bulk delivery is almost always cheaper — use the bulk-material cost calculator to compare once you know your volume.
Formula
Mulch is a slab of material, so its volume follows directly from area and depth:
cubic yards = area (sq ft) × depth (in) ÷ 324
bags = ceil( cubic yards × 27 ÷ bag size in cu ft )
The constant 324 is not arbitrary: there are 27 cubic feet in a cubic yard, and a foot is 12 inches, so 27 × 12 = 324. Dividing by it converts square-feet-times-inches straight into cubic yards. A standard 2 cu ft bag means one cubic yard is 27 ÷ 2 = 13.5 bags — the number you will see quoted on coverage charts.
Worked example
Say you have 300 sq ft of beds and want a 3 in layer using 2 cu ft bags:
- Volume:
300 × 3 ÷ 324 = 2.78 cu yd - Bags:
2.78 × 27 ÷ 2 = 37.5, rounded up to 38 bags
So 300 sq ft at 3 inches is about 2.78 cubic yards, or 38 bags. At that volume a bulk yard would be worth pricing against 38 bags.
Getting the mulch order right
A few practical points that keep the estimate honest:
- Buy a little extra. Beds are rarely perfect rectangles and mulch settles as it weathers, so add about 5–10% to the volume above.
- Depth matters more than you think. Going from 2 in to 3 in is a 50% jump in volume and cost — measure the depth you actually want.
- Do not pile mulch on trunks. Keep mulch a few inches off stems and trunks; a “mulch volcano” rots bark. For a tree ring, use the mulch-ring calculator, which subtracts the open center.
- Bag size varies. Bark mulch is often 2 cu ft, but rubber and some hardwood mulches come in 1.5 or 3 cu ft bags — set the bag size to match, and always confirm the coverage printed on the bag before you order.
Want the reasoning end to end? The how-much-mulch guide walks through measuring an irregular yard, choosing a depth, and deciding between bags and bulk.
Reference table
Cubic yards of material by area and depth (cu yd = area × depth ÷ 324). Bulk materials are usually sold by the cubic yard or ton, so round up and buy about 5–10% extra.
| Depth | 100 sq ft | 300 sq ft | 500 sq ft | 1,000 sq ft |
|---|---|---|---|---|
| 1 in | 0.31 cu yd | 0.93 cu yd | 1.54 cu yd | 3.09 cu yd |
| 2 in | 0.62 cu yd | 1.85 cu yd | 3.09 cu yd | 6.17 cu yd |
| 3 in | 0.93 cu yd | 2.78 cu yd | 4.63 cu yd | 9.26 cu yd |
| 4 in | 1.23 cu yd | 3.70 cu yd | 6.17 cu yd | 12.35 cu yd |
| 6 in | 1.85 cu yd | 5.56 cu yd | 9.26 cu yd | 18.52 cu yd |
See the full breakdown, including bags per cubic yard, on the material-coverage table.