GardenCalc

Mulch Calculator

Work out exactly how much bark, wood chip, compost or decorative mulch you need for your beds and borders. No guesswork, no wasted bags.

Calculate Your Mulch

Choose your area shape, enter dimensions and mulch depth — we'll tell you the volume and how many bags to buy.

Your Results

Volume
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Volume
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Litres
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60-Litre Bags
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Approx. Weight
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How Much Mulch Do I Need?

This free mulch calculator works out exactly how much bark, wood chip, compost or decorative mulch you need for any garden bed or border. Choose your area shape — rectangular, circular or irregular — enter the dimensions and mulch depth, and get an instant answer in cubic metres, litres, bag counts and approximate weight.

Stop buying too many bags or running short halfway through. Get the right amount first time and save yourself extra trips to the garden centre.

Recommended Mulch Depths by Type

Different mulch types work best at different depths. Use this guide to choose the right depth for your project.

Mulch Type Depth (cm) Depth (inches) Notes
Bark chippings 5–7.5 2–3 Best all-round mulch, lasts 2–3 years
Composted bark 5–7.5 2–3 Enriches soil as it breaks down
Wood chip 7.5–10 3–4 Cheaper but decomposes faster
Decorative gravel 3–5 1–2 Lay over weed membrane, lasts indefinitely
Compost mulch 5–10 2–4 Feeds plants, breaks down in 1 season
Straw / hay 10–15 4–6 Good for veg plots, settles quickly

Frequently Asked Questions

How much mulch do I need for a garden bed?
The amount depends on your bed size and mulch depth. For a typical 3m × 1.5m border mulched to 7.5cm (3 inches) deep, you need about 0.34 cubic metres — roughly 340 litres or 6 bags of 60-litre bark. Use the calculator above with your exact dimensions for a precise figure.
How deep should mulch be?
Most organic mulches like bark and wood chip should be applied 5–7.5cm (2–3 inches) deep. This is thick enough to suppress weeds and retain moisture without smothering plant roots. Decorative gravel is usually 3–5cm over a weed membrane. Avoid going deeper than 10cm with bark or compost as it can prevent water reaching the soil.
How many bags of bark chippings do I need?
A standard 60-litre bag of bark chippings covers about 0.8 square metres at 7.5cm deep. For a 10 square metre border, you would need roughly 13 bags. For larger areas over 1 cubic metre, consider buying a bulk bag (typically 1m³) — it's usually much cheaper per litre than individual bags.
What is the best mulch for UK gardens?
Bark chippings are the most popular mulch in UK gardens. They suppress weeds effectively, retain moisture, look tidy, and last 2–3 years before needing a top-up. Composted bark is even better for borders as it slowly enriches the soil. For low-maintenance or Mediterranean-style gardens, decorative gravel over a weed membrane is a good permanent option.