Calculate how much bark, wood chip or composted mulch you need to cover beds and borders. Enter the area, choose a depth, and get litres, cubic metres and the best-value bags to buy.
A 5cm layer is enough to suppress weeds and lock in moisture. One bulk bag (around 730L) covers roughly 14m² at that depth.
01 — The Calculator
Pick a material, pace out your plot, and the value engine prices every way to fill it — hippo bags, dumpy bags or handy sacks.
Enter dimensions to calculate.
Volume
0 litres
Cubic
0.00 m³
Area
0.0 m²
Est. weight
0.00 tonnes
Best price
—
Enter your plot size below — we'll price the cheapest way to cover it.
5 cm
Depth changes the volume a lot — 5cm mulch is normal, raised veg beds want 20cm+.
Not sure? See the depth guide belowWhy allow extra? See why soil settles after laying
Worked example: mulched border
A border 8m long by 1.5m wide (12m²) mulched 5cm deep needs 12 × 5 × 10 = 600 litres. One bulk bag does the job with a little to spare; handy bags would mean 9 × 70L bags at a higher price per litre.
The golden rule for weed suppression is 5–7.5cm over bare, weed-free soil — thinner than 5cm lets enough light through for weeds to punch back, while deeper than 10cm around plants risks collar rot. Always hoe off existing weeds first; mulch smothers seedlings, not established perennial roots. Keep the mulch a few centimetres clear of stems and trunks, and water the ground well before spreading if the soil is dry.
Bark chips last two to three years and stay tidier on borders; wood chip is cheaper but breaks down faster and suits paths and allotments. Either way, expect to top up by roughly a third each spring as the layer settles and rots down — that feeding of the soil is half the point. For play areas, use certified play bark at 10–15cm for impact absorption, not decorative mulch. A bulk bag of around 700–1,000 litres covers about 13m² at 7.5cm, so beyond a couple of beds it beats handy bags on price.
5–7.5cm is ideal for weed suppression and moisture retention. Less than 5cm lets weeds through; more than 10cm can suffocate roots. Our mulch depth guide breaks it down by plant type.
Last reviewed: October 2026 · Reviewed by the Garden Calculator editorial team.
Garden Calculator — Project
My garden project · 28 October 2026
| Item | Qty | Each | Total |
|---|---|---|---|
| Estimated total | £0.00 | ||
Prices from the Garden Calculator sample trade catalogue — confirm with your merchant before ordering.