Bark Calculator
Find the litres and bags of bark mulch or decorative bark chippings for a garden bed or border.
Measure your project
Your answer
That covers 8 m².
If you buy bags
If you buy bulk bags
The RHS says lay bark mulch at least 50 mm thick, and ideally 75 mm.
Which costs less?
That is 6 bags to carry. For a small job, bags are easy.
100 litre bag: £13 with VAT at 2 sellers. 500 litre bulk bag: £122.23 with VAT, the middle of 3 prices from only 2 sellers (Oct 2026). Treat both as rough guides.
Quick answers
- A 4 × 2 m border, 75 mm deep
- About 600 litres of bark. That is 6 bags of 100 litres, or 2 bulk bags of 500 litres.
- How deep?
- At least 50 mm, and ideally 75 mm, says the RHS.
- Per m²
- 50 litres at 50 mm deep, or 75 litres at 75 mm.
- One 100 litre bag
- Covers 2 m² at 50 mm, or 1.33 m² at 75 mm.
How to work it out
- Measure the bed in metres. Length × width gives the area in m².
- Pick a depth in mm and divide it by 1,000 to get metres.
- Area × depth gives the bark you need in m³.
- Multiply m³ by 1,000 to get litres. Bark is sold by the litre.
- Divide the litres by the bag size (100 or 500 litres). Round up.
4 × 2 × 0.075 = 0.6 m³
0.6 × 1,000 = 600 litres
600 ÷ 100 = 6 bags, or 600 ÷ 500 = 1.2 → 2 bulk bags
How much bark per square metre?
Use this easy rule to work out how much bark to use. Each mm of depth over 1 m² takes 1 litre of bark. So 75 mm deep is 75 litres per m².
| Depth | Litres per m² | 100 litre bag | 500 litre bag | 1 m³ |
|---|---|---|---|---|
| 25 mm | 25 | 4 m² | 20 m² | 40 m² |
| 50 mm | 50 | 2 m² | 10 m² | 20 m² |
| 75 mm | 75 | 1.33 m² | 6.7 m² | 13.3 m² |
| 100 mm | 100 | 1 m² | 5 m² | 10 m² |
The litres work the same for wood chip. The weight may not, as we only have a weight for bark.
How deep should bark be?
- RHS: bark and other mulch at least 50 mm thick, and ideally 75 mm.
- Melcourt (a UK bark maker): 75–100 mm for its bark mulch. It allows 5–10% extra, as bark settles.
- B&Q's bag cover of 4 m² per 100 litres is for a 25 mm top-up. For a new bed, it covers far less.
The RHS says to mulch from mid to late spring, and in autumn. For bark under a swing or slide, see our play bark calculator. It needs a much deeper layer.
Bark for common bed sizes
All rows are 75 mm deep, the RHS ideal. Add 5–10% if you want extra for settling.
| Bed | Litres | 100 litre bags | 500 litre bulk bags |
|---|---|---|---|
| 2 × 1 m | 150 | 2 | 1 |
| 3 × 1 m | 225 | 3 | 1 |
| 4 × 2 m | 600 | 6 | 2 |
| 5 × 2 m | 750 | 8 | 2 |
| 10 × 1 m | 750 | 8 | 2 |
UK bark bag sizes and prices
Bark is sold by the litre. These are the sizes we found:
- 100 litre bags: £13 at Wickes and B&Q, with VAT. Multi-buys cut it: Wickes does 3 for £30, so £10 a bag.
- 500 litre bulk bags: £110 to £124 with VAT (one on sale) at Wickes and Lawsons.
- Other sizes: Melcourt sells its bark in 600 litre bulk bags, or loose. Rolawn sells up to 750 litres.
Per m³, our 100 litre bag price works out at £130. Bulk bags work out at £220–£248. So at these prices, 100 litre bags cost less per m³, but you carry more of them.
There are only a few sellers here, so check local prices too.
Laying bark: weed membrane or not?
The RHS says a sheet mulch or woven landscape fabric can be used on new beds. Some call it a weed barrier. Lay it on the ground, plant through slits, then hide it under the bark. It is a choice, not a must.
Pick a sheet that lets water through. The RHS says a waterproof one can make rain run off.
Want stone instead of bark? See our slate chippings calculator.
Questions people ask
How much bark mulch do I need?
Multiply the area in m² by the depth in mm. That gives litres. A 4 × 2 m border at 75 mm needs 600 litres: 6 bags of 100 litres.
How much bark per square metre?
50 litres at 50 mm, the RHS's least depth. At its ideal 75 mm, it is 75 litres per m².
How do you work out bark mulch coverage?
Divide the litres by the depth in mm to get m². So 100 litres at 50 mm covers 2 m². One m³ covers 20 m² at 50 mm.
How much does a 100L bag of bark chippings cover?
2 m² at 50 mm, or 1.33 m² at 75 mm. B&Q prints 4 m², but that is only 25 mm deep.
How many bags of bark chips do I need?
Divide the litres you need by the bag size. A 4 × 2 m border at 75 mm needs 600 litres. That is 6 bags of 100 litres.
How many litres of bark are in a bulk bag?
Wickes sells 500 litre bulk bags. Melcourt sells 600 litres, and Rolawn up to 750 litres. Bark bags are sold by litres, not by the tonne.
How many litres are in a tonne of bark?
About 4,000 litres. A 500 litre Wickes bag weighs about 125 kg. That is one bag's figure, so treat it as a rough guide.
Do I need to put a weed membrane under bark?
No, the RHS says it is a choice. It says a woven landscape fabric can be used under bark on new garden beds. Pick one that lets water through.
Where our numbers come from
- Mulch depth and membranes: RHS mulch guide
- Bark depth 75–100 mm, 5–10% settling: Melcourt
- Bark weight: Wickes 500 litre bark bag (about 125 kg)
- Bark bag prices: Wickes 100 L and 500 L bags
- Bark 100 L bag: B&Q Verve (4 m² at 25 mm)
- Bark 500 litre bulk bag: Lawsons £122.23
- Bark bulk bags of 0.5 and 0.75 m³: Rolawn
Made by BuildersCount. Last checked 4 Oct 2026.
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