Mulch & Topsoil Calculator

How it works

Mulch or topsoil is an area covered to a depth: volume = surface × depth. Because depth is in centimetres and area in square metres, convert first — 20 m² at 5 cm is 20 × 0.05 = 1 m³, which equals 1,000 litres. The recommended depth depends on the job. Around 5–8 cm suppresses weeds and holds moisture in beds; 2–3 cm is enough as a decorative top layer; and thicker than about 10 cm can suffocate roots by blocking air and water. Keep mulch a few centimetres clear of trunks and stems to avoid rot. Remember that organic mulch settles and decomposes — expect to top it up each year, which is also how it feeds the soil. Bagged products are sold in litres and bulk deliveries in cubic metres; the 1 m³ = 1,000 L conversion is what lets you compare the two prices honestly.