1. Home
  2. Garden
  3. Mulch calculator

Mulch calculator

Work out how much bark or mulch you need for your borders or a children's play area. You get the volume in m³ and litres, the number of bags in the size you plan to buy, and the number of bulk bags.

Man raking bark mulch around shrubs in a garden border with a wheelbarrow
Your result

Mulch needed

1 m³

1,000 litres at 50 mm deep. 1 m³ is 1,000 litres.

Litres
1,000 litres
50 litre bags
20rounded up to whole bags
Bulk bags (500 litre)
2
Bulk bags (750 litre)
2
Approximate weight
350 kgbark is heavier when wet

Add this to your project shopping list, then print it or take it to the merchant.

Open shopping list

How to use the mulch calculator

  1. Choose the Shape of the area: a rectangle, circle, triangle, or enter the area if you know it.
  2. Measure it and enter the sizes. Each box has its own unit, so you can use metres or feet.
  3. Under What is it for? pick garden borders and beds (50 mm), children's play area bark (300 mm), or enter your own depth.
  4. Pick the Material: bark chippings or mulch, or compost or soil improver.
  5. Choose the Bag size you will buy in litres. Check the litres printed on the bag.
  6. Read the bag counts and the weight, then tap Add to shopping list or Share link.

Why use this calculator

It speaks in litres and bags. UK sellers say bark, woodchip and play bark, and they sell it in bags of 50 to 100 litres or in 500 and 750 litre bulk bags. The calculator gives the count for each.

It has a separate setting for play areas. Play bark goes down much deeper than border mulch, so a play area needs several times the amount per m².

It stays in metric and shows its working, so you can check the sums against a bag.

How we worked it out

Your numbers, step by step. This updates as you change the calculator.

  1. Area = length × width = 5 m × 4 m = 20 m²
  2. Volume = area × depth = 20 m² × 0.05 m = 1 m³ (1,000 litres)
  3. Bags = 1,000 litres ÷ 50 litres per bag = 20 bags
  4. Bulk bags = 1 m³ ÷ 0.5 m³ (500 litre bag) = 2, or ÷ 0.75 m³ (750 litre bag) = 2

The formula

The volume of mulch is the area times the depth in metres. Then convert to litres.

Volume (m³) = area × depth Litres = m³ × 1,000

A 10 m² border at 50 mm (0.05 m) deep is 0.5 m³, which is 500 litres.

  • Bags: litres ÷ litres per bag, rounded up. For 500 litres in 50 litre bags that is 10 bags.
  • Bulk bags: m³ ÷ 0.5 for a 500 litre bag, or m³ ÷ 0.75 for a 750 litre bag, rounded up. For 0.5 m³ that is 1 bag either way.
  • Weight: volume × about 350 kg per m³ for bark. For 0.5 m³ that is about 175 kg.

What we assume

  • Border mulch is 50 mm deep. This is the supplier standard, and 75 mm is a common upper end for weed control. Play areas are laid at 300 mm, as quoted by play bark suppliers.
  • Bark weighs about 350 kg per m³. Real bark ranges from about 330 to 400 kg per m³, and wet bark is heavier.
  • Compost is taken as 0.5 tonnes per m³ as a rough midpoint. UK figures vary a lot with the type and how wet it is, so for compost work in litres and ignore the weight.
  • Bulk bags are 500 or 750 litres. Retail bags vary, so check the label.

Tips

  • Check the litres on the bag, not the picture. Bag sizes differ between brands, and compost bags in particular vary.
  • Check the depth with a ruler in a few places as you spread. It is easy to put down more or less than you planned.
  • For a play area, check the surfacing depth your play equipment needs. The calculator's 300 mm is a starting point from play bark suppliers.
  • Wet bark is heavier than dry, so check the weight if you are carrying it or if a delivery has to be moved by hand.
  • Preparing beds first? The topsoil calculator works out how much soil goes under the mulch.

FAQs

How much bark or mulch do I need per m²?
50 litres per m² at the standard 50 mm depth, so a 50 litre bag covers 1 m². Some people go to 75 mm to hold back weeds, which is 75 litres per m².
How deep should mulch be on a garden border?
50 mm is the usual supplier depth. Some people go up to 75 mm to hold back weeds, but that is a rule of thumb, not a supplier figure.
How many litres of bark are in a cubic metre?
1,000 litres. So 1 m³ is 20 bags of 50 litres, and a 500 litre bulk bag is half a cubic metre.
How many 50 litre bags of mulch do I need for 10 m²?
10 bags at 50 mm deep, because 10 m² × 0.05 m is 0.5 m³, which is 500 litres. A single 500 litre bulk bag does the same job.
How much play bark do I need for a children's play area?
About 300 litres per m² at the 300 mm that play bark suppliers quote. A 10 m² area needs 3 m³, which is 60 bags of 50 litres, or 4 bulk bags of 750 litres. Check the depth your play equipment calls for.
How much does a bulk bag of bark cover?
A 500 litre bulk bag covers about 10 m² at 50 mm, and a 750 litre bag covers about 15 m². At the 300 mm play depth, a 500 litre bag covers only about 1.7 m².

Last reviewed: 6 November 2026 · How we calculate · Report an error