The formula (and the trap)
Volume itself is simple — length × width × depth. The trap is units: beds are measured in feet, depth in inches, bulk soil sold by the cubic yard, and bags by the cubic foot. One missed conversion and your order is off by a factor of three. This calculator keeps every unit straight and totals across multiple beds.
cubic ft = L(ft) × W(ft) × depth(in) ÷ 12 · cubic yards = cubic ft ÷ 27
Reference depths that work
| Use | Depth | Notes |
|---|---|---|
| New raised bed (vegetables) | 10–12″ | Full root depth for tomatoes, carrots, brassicas |
| Topping up an existing bed | 2–3″ | Annual refresh of compost each spring |
| Mulching beds & paths | 2–3″ | Weed suppression without smothering soil |
| New lawn topdressing | 0.5–1″ | Thin, even layer raked into turf |
| Sheet-mulch / no-dig start | 4–6″ | Compost layer over cardboard |
Bags or bulk?
A cubic yard is 27 cubic feet — about 13½ of the big 2-cubic-foot bags. Under half a yard, bags are usually easier and not much pricier. Above a yard, bulk delivery gets dramatically cheaper per yard, at the cost of a soil pile in the driveway and a wheelbarrow afternoon. Filling a standard 4×8 bed a foot deep takes about 1.2 yards — right at the crossover point.
Frequently asked questions
How deep should I fill a raised bed?
For most vegetables, 10–12 inches of good soil is the sweet spot — enough for tomato and carrot roots. Shallow-rooted greens manage with 6–8 inches, and beds on hard ground or concrete want the full 12+. If the bed sits on decent native soil, roots will continue down into it.
How much mulch do I actually need?
Spread 2–3 inches for weed suppression and moisture retention — more than 4 inches can smother soil life and shed water. Enter your bed or path area with a 3-inch depth above and you’ll get the cubic yards to order.
Is it cheaper to buy soil in bags or in bulk?
Bulk wins on price once you need roughly a cubic yard or more (that’s ~13½ two-cubic-foot bags). Bags win on convenience, consistency, and small quantities. The calculator shows both counts so you can price each option locally.
How much does a cubic yard of soil weigh?
Roughly 1,000–1,400 lbs for dry topsoil or garden mix, and up to 2,000+ lbs wet. That’s beyond most pickup half-ton ratings for a single yard, which is why bulk soil usually arrives by dump truck or a heavy-duty trailer.