Free garden calculator

Raised-bed compost calculator.

Measure the space you actually need to fill. Get the volume, material split and bag count without wrestling with unit conversions.

  • Metric or imperial
  • Multiple beds
  • No signup

1 · Measure the inside

Your raised bed

Measurement units

2 · Choose the materials

Your fill mix

Mix total: 100%

3 · Compare bags

Optional cost

Total material to order

950 litres0.95 cubic metres

Material split

What to order

60%Topsoil

570 litres · 0.57

30%Compost

285 litres · 0.29

10%Other amendment

95 litres · 0.1

Bag comparison

If buying small bags

40 L bags
24
50 L bags
20
60 L bags
16

Or roughly 2 × 700 L bulk bags. Supplier bulk-bag volumes vary, so check the listing.

Selected bag order20 × 50 L
Very rough filled weight7031,064 kg

Not suitable for structural loading decisions.

Base volume before settlement: 864 litres. The result includes your 10% allowance and rounds bag quantities up.

Measure carefully

Use the internal dimensions.

Measure inside the boards, then enter only the depth that still needs filling. If a bed already contains 20 cm and you want 30 cm, the calculator orders the missing 10 cm—not the full frame.

Understand the estimate

Volume is firm. Weight is not.

The volume uses length × width × missing depth. The handling-weight range is deliberately broad because moisture, texture and compaction vary by product.

Calculation notesA 10–20% settlement option reflects common UK supplier guidance. Density assumptions use a broad compost range of 300–600 kg/m³ and topsoil range of 1,000–1,400 kg/m³.Settlement guidance ↗Topsoil density reference ↗