Free materials calculator

Bark Chippings & Mulch Calculator

Enter each bed length, width and spread depth to get the volume of bark chippings, bark mulch or compost in cubic metres - plus how many bags to buy. Works in metres and centimetres.

Showing results for United Kingdom

Areas & depth

01. Areas

Length (m)

Width (m)

Spread depth (cm)

02. Supply

Bag size

Typical depths: 50–75 mm (2–3 in) for mulch, 40–50 mm for decorative gravel, 100 mm (4 in)+ for new topsoil, deeper again to fill a raised bed. Each area can take its own depth.

Cost (optional)

Price per m³ · 0.50 m³ (£)

Enter the delivered price per m³ of bulk material to get the total.

Calculated requirement

0.50m³ of material

Total bed area

10.00 m²

In litres

500 L

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Guide & worked example

How this calculator works

Mulch is spread to an even depth, so the amount you need is simply the bed area times the depth:

volume = length × width × depth

The calculator reports that volume in cubic yards or cubic metres (and litres or cubic feet), then divides by the size of one bag to give the number of bags. Add a bed for each area you are covering - a border, an island bed, a path edge - and the volumes pool into one order. All math runs in exact metric internally, so switching units never changes the answer.

Worked example

This example follows the unit system you pick in the calculator above.

A 4 m × 2.5 m bed at 50 mm deep, using 50-litre bags:

Bed area: 4 × 2.5 = 10 m².
Volume: 10 × 0.05 = 0.5 m³ = 500 litres.
From 50-litre bags: 500 ÷ 50 = 10 bags.

Mulch depth guide

Job	Depth	Notes
Bark / wood-chip on beds	50–75 mm (2–3 in)	Keep clear of stems
Around trees	75–100 mm (3–4 in)	Leave a gap at the trunk
Weed suppression	75 mm (3 in)	Over a clear, weeded bed
Top-up of existing mulch	25–50 mm (1–2 in)	Mulch breaks down yearly

Tips for ordering

Bulk mulch settles - order a touch generous rather than short for a second delivery.
For irregular beds, split them into rectangles, add a bed per rectangle, and the calculator totals them.
Mulch breaks down over a season or two, so budget to top up beds roughly once a year.
Covering a driveway or path instead? Use the Gravel Calculator. Laying new lawn or filling beds with soil? Use the Topsoil or Raised Bed Soil calculators.

Frequently asked questions

How much mulch do I need for a garden bed?

Multiply the bed area by the depth. A 4 m × 2.5 m bed at 50 mm deep needs 0.5 m³ (500 litres), which is ten 50-litre bags. Enter your bed and depth above for the exact figure.

How deep should mulch be?

Spread mulch 50–75 mm deep for beds and borders - enough to suppress weeds and hold moisture without smothering roots. Keep it clear of plant stems and tree trunks. Going much deeper wastes material and can starve roots of air.

How many bags of mulch are in a cubic metre?

A cubic metre is twenty 50-litre bags, or forty 25-litre bags. Once you need more than about ten bags, ordering in bulk by the cubic metre is usually cheaper.

Should I buy mulch in bags or in bulk?

Bags suit small beds and are easy to handle and store. Bulk delivery by the cubic metre is cheaper per unit and better for large areas, but you need somewhere to tip it and the labour to barrow it. The calculator gives both a bag count and a bulk volume so you can compare.

Do you have a topsoil or gravel calculator?

Yes - the volume math is the same, but each material spreads to a different depth and is sold differently. Use the dedicated Topsoil Calculator for lawns and beds, the Gravel Calculator for driveways and paths, or the Raised Bed Soil Calculator to fill raised beds. Links are in the related tools below.

Related guides

How Much Mulch Do I Need?

The depth guide and formula for buying the right amount of mulch.

Read guide→