Gardening
Topsoil Calculator
Enter length, width and depth to estimate volume, bags and optional cost.
Topsoil
Topsoil orders fail when depth is guessed wrong: a lawn top-dress needs a thin skim, while a new bed or raised fill can take many centimetres across the same footprint. Enter length, width and fill depth to get cubic volume, add a little extra for settling after the first watering, then divide litres by the bag size on the compost or topsoil you actually buy. Screening grade and whether stone is removed are not modelled — only how much space you are filling. Once volume is sorted, plan plant spacing with garden tools such as the garden area calculator and mulch depth with the mulch calculator.
Worked example
A 5 × 3 m bed at 10 cm is 1.5 m³ before waste. With 10% extra ≈ 1.65 m³ (1,650 L). At 25 L per bag that is 66 bags.
Limits and assumptions
Quality, pH and nutrient content are not assessed. Layered builds (drainage under growing medium) need separate volumes for each layer.
Frequently asked questions
How deep for new turf?
Suppliers often recommend a few centimetres of screened topsoil over prepared ground — check their sheet rather than copying a bed depth.
Raised beds versus open ground?
Measure the internal length × width × the depth you will fill. Timber walls are not part of the volume.
Can I mix topsoil and compost bags?
Work in total litres needed, then buy any mix of bag sizes that reaches that volume.
Why add waste for soil?
Fine mixes settle after watering and edges get skimmed thin — a small extra stops a second trip.