Garden soil
Enter your bed size and depth to get the exact soil volume — total cubic feet, bulk cubic yards, how many bags to buy, and an optional soil-mix breakdown you can take to the store.
Soil needed
—Enter bed size and depth to estimate soil.
| Total volume | — |
|---|---|
| Bulk (cubic yards) | — |
| Bags to buy | — |
| Volume (litres) | — |
| Estimated cost | — |
Soil mix breakdown
| Component | Cu ft | Bags |
|---|
Soil volume is just length × width × depth (for a round bed, π × radius² × depth). We convert everything to feet, so the result is in cubic feet, then divide by 27 for cubic yards and by your bag size for the bag count. Bag counts are always rounded up.
Below about a cubic yard, bagged soil is easiest. Past that, bulk delivery is usually cheaper per cubic foot — the calculator shows both so you can decide. Remember fresh compost settles, so topping up after the first season is normal.
Standard volume math; 1 cubic yard = 27 cubic feet. Estimates only.
Straight topsoil packs down and drains poorly; pure compost settles by a third as it breaks down. A blended mix — compost plus something for structure and something to hold moisture — keeps the bed loose and productive.
Fresh compost settles noticeably in the first season, so budget for a 1–2 inch top-up next spring rather than being surprised by a sunken bed. It's normal, not an error in your math.
If you line the bottom with logs, branches, or coarse filler, you need less soil than the frame height suggests. Enter the actual soil depth above the filler so you don't over-order.
Building several identical beds? Set the bed count so the total, bag count, and bulk figure cover the whole project — it's an easy way to end up one delivery short.
Multiply length × width × depth to get the volume. For a 4 × 8 ft bed filled 10 inches deep that is about 26.7 cubic feet — roughly 18 bags of 1.5 cu ft soil, or about 1 cubic yard in bulk. Use the calculator for your exact size.
Divide the total cubic feet by the bag size and round up. A common 1.5 cu ft bag fills 1.5 cubic feet, so a 26.7 cu ft bed needs ceil(26.7 ÷ 1.5) = 18 bags. The calculator lets you switch bag sizes (0.75, 1, 1.5, 2, 3 cu ft).
Bagged soil is convenient for one or two small beds, but once you need roughly a cubic yard (about 18 bags of 1.5 cu ft) bulk delivery is usually cheaper per cubic foot. The calculator shows both the bag count and the bulk cubic-yard figure so you can compare.
Mel's Mix, from square-foot gardening, is equal parts (by volume) compost, peat moss or coco coir, and coarse vermiculite. Pick it in the soil-mix dropdown and the calculator splits your total into the three components and the bags of each you need.
Most vegetables are happy with 6–12 inches of soil; deep-rooted crops like carrots, potatoes, and tomatoes prefer 12–18 inches. Enter the actual depth you'll fill, which isn't always the frame height — if you put coarse filler in the bottom, count only the soil above it.
Don't fill a raised bed with bagged garden soil or straight topsoil — it packs down, drains poorly, and crusts over. Use a raised-bed mix or blend your own, like Mel's Mix (equal parts compost, peat or coco coir, and vermiculite), for drainage and nutrients.
Organic matter breaks down and beds settle, so most gardeners add 1–2 inches of compost or mix each spring — that's bed area × depth for the top-up. The drop is biggest after the first season, so plan to refill then.
Estimate only, based on the dimensions you enter and standard volume math. Real fill varies with settling, compaction, and supplier bag sizes. Bag counts are rounded up. Confirm against your supplier's coverage before ordering.