Enter each bed length, width and spread depth to get the volume of mulch or bark in cubic yards or cubic metres - plus how many bags to buy. Works in feet/inches or metres/centimetres.
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.
Total bed area
10.0 sq ft
In cubic feet
4.2 cu ft
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.
This example follows the unit system you pick in the calculator above.
A 12 ft × 9 ft bed at 2 inches deep, using 2-cubic-foot bags:
| 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 |
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. In US units, a 13ft × 8ft bed at 2 inches deep is about 0.65 cubic yards. Enter your bed and depth above for the exact figure.
Spread mulch 50–75 mm (2–3 inches) 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.
A cubic yard is about 13–14 bags at 2 cubic feet each, or 9 bags at 3 cubic feet. In metric, a cubic metre is twenty 50-litre bags. Once you need more than about ten bags, ordering in bulk by the cubic yard or metre is usually cheaper.
Bags suit small beds and are easy to handle and store. Bulk delivery by the cubic yard or 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.
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.
Want this page set up for your region?