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Topsoil Calculator

Find how much topsoil you need.

How it is calculated

Treat the bed as a box: volume = length × width × depth, with all three in metres, giving cubic metres. Litres are volume × 1000, and bags are ⌈ litres ÷ 25 ⌉, rounded up because bags are sold whole. The depth is the thickness of the soil layer you want to spread, so it is usually a small number such as 0.1 or 0.15 m, not centimetres. Volume is shown to three decimals. Settling and compaction are not included, so many gardeners add a little extra. All three sizes must be above zero.

Worked example

A bed 4 m long, 1.5 m wide, topped up 0.15 m deep. Volume = 4 × 1.5 × 0.15 = 0.900 m³. Litres = 0.9 × 1000 = 900 L. Bags of 25 L = 900 ÷ 25 = 36 bags exactly, so you need 36.

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Common mistakes

  • Entering depth in centimetres (15) instead of metres (0.15), which gives a hundred times too much soil.
  • Mixing metres for length and feet for width.
  • Forgetting that bag size here is fixed at 25 L; larger bags change the count.
  • Not allowing extra for settling or uneven ground; the figure is for a perfectly level layer.
  • Ordering by bag count for a large area where loose delivery by the cubic metre is cheaper; use the m³ figure then.

About this calculator

This calculator multiplies bed length × width × depth to find the volume of topsoil needed for a garden bed or lawn, converting the result into cubic meters, liters, and the number of standard 25-liter bags to buy (rounded up since partial bags aren't sold). Depth is the dimension most often underestimated — a bed that looks small in area can still need a surprising volume once a proper 10-15 cm topsoil layer is factored in.

Gardeners, landscapers, and homeowners starting a new lawn or raised bed use it to budget the right amount of topsoil (or compare bagged vs. bulk-delivered pricing) before a trip to the garden center. Enter the bed's length, width and depth to get the volume and number of bags needed.

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