Mulch Calculator

What this means

Mulch volume is length × width × depth. The depth matters more than with soil — too thin a layer doesn't suppress weeds or hold moisture, and too thick a layer can smother plant roots. A common target is 5–10 cm (2–4 inches). After adding a waste allowance, we convert the volume into standard bags so you can buy without a calculator in the garden centre.

Recommendations

• •Aim for 5–10 cm (2–4 in) of mulch — thinner won't suppress weeds, thicker can harm roots.
• •Spread mulch in spring and top up in autumn; it breaks down and feeds the soil.
• •Keep mulch a few centimetres clear of plant stems and tree trunks to prevent rot.

Watch out

• •Don't pile mulch against tree trunks — 'mulch volcanoes' trap moisture and cause decay.
• •Heavy wood mulch uses soil nitrogen as it breaks down; this is rarely a problem for established beds.