Topsoil Calculator
Topsoil volume, bags, and delivery weight from bed size.
What it does
Topsoil math surprises new gardeners. A modest bed at a few inches deep still weighs over a ton, which decides bags versus delivery.
The tool above turns bed size into volume, bags, and weight. Ten by eight feet at 4 in is 26.7 ft3, or 54 bags weighing 1.3 tons. The metric match is 3 by 2.4 m at 10 cm for 0.72 m3 and 29 bags.
Depth sets the job. Two inches topdresses tired lawns, 4 to 6 in builds beds, and a foot fills raised boxes to the brim.
Bags suit small patches. Fifty four bags stack on one pallet run, while bulk yards dump cheaper for whole lawns.
Weight plans the path. Ton loads need driveway drops and wheelbarrow crews, not trunk trips.
How to use
- Pick imperial (ft, in) or metric (m, cm).
- Enter bed length and width.
- Enter depth: 4 in or 10 cm suits topdressing.
- Read volume first.
- Read bags next.
- Read weight and book delivery for tons.
Formula
- L
- Bed length.
- W
- Bed width.
- depth
- Soil depth.
Bags are 40 lb imperial and 25 L metric. Metric tonnes run 1.35 per m3 with the same round up rule.
Worked example
Example: 10 by 8 ft, 4 in deep
Imperial defaults: 10 by 8 ft bed at 4 in deep. These are also the default values, so the page opens on this answer.
- Bed: 10 by 8 ft at 4 in deep.
- Feet: 4 / 12 = 0.3333 ft.
- Volume: 10 x 8 x 0.3333 = 26.7 ft3.
- Bags: ceil(26.7 / 0.5) = 54 bags.
- Weight: 26.7 x 0.05 = 1.3 tons.
- Tool shows 26.7 ft3, 54 bags (40 lb), 1.3 tons.
Reference table
| Bed | Volume | Bags |
|---|---|---|
| 8 by 6 ft, 3 in | 12 ft3 | 24 bags (40 lb) |
| 10 by 8 ft, 4 in | 26.7 ft3 | 54 bags (40 lb) |
| 20 by 10 ft, 6 in | 100 ft3 | 200 bags (40 lb) |
| 3 by 2.4 m, 10 cm | 0.72 m3 | 29 bags (25 L) |
Limits
- Volume math only. Soil quality needs sourcing.
- Settling eats about a tenth.
- Wet soil weighs more than dry math.
- Delivery access needs planning.
Common mistakes
- Eyeballing depth across humps.
- Bags for multi yard lawns.
- No extra for settling.
- Trunk hauling ton loads.
- Skipping soil tests on fill dirt.
Try it yourself
Quick checks. Answers sit tucked under each question.
8 by 6 ft at 3 in?
8 x 6 x 3/12 = 12 ft3. Bags are ceil(12 / 0.5) = 24 bags. Weight is 12 x 0.05 = 0.6 tons.
2 by 2 m at 15 cm metric?
2 x 2 x 0.15 = 0.6 m3. Bags are ceil(0.6 / 0.025) = 24 bags. Weight is 0.6 x 1.35 = 0.8 tonnes after rounding (0.81).
Questions
How much soil volume?
Multiply length by width by depth in feet. Here 10 x 8 x 4/12 = 26.7 ft3.
How many bags?
Divide volume by 0.5 ft3 per 40 lb bag and round up. Here ceil(26.7 / 0.5) = 54 bags.
How heavy a delivery?
Multiply volume by 0.05 tons. Here 26.7 x 0.05 = 1.3 tons.
Bags or bulk?
Bulk wins past a yard. Bags suit small beds, bulk piles suit new lawns.
Order extra?
Yes. Settle and compaction eat a tenth, so order a little long.
Does this fix bad soil?
No. Contaminated ground needs testing first.