FREE GARDEN MATERIAL CALCULATOR · METRIC
Mulch Calculator & Bag Estimator
Calculate how much mulch a garden bed or border needs from its area and planned depth, then convert the result into litres, cubic metres and the number of bags to buy.
MULCH VOLUME CALCULATOR
Work out litres, cubic metres and bags before you buy.
Enter the area to cover, the mulch depth you plan to use and the bag size sold by your supplier. Add an optional allowance for uneven ground, settling or measurement uncertainty.
FORMULA
litres = area (m²) × depth (cm) × 10 · total = litres × allowance · bags = total litres ÷ bag size, rounded upArea and depth become volume.
For metric measurements, one square metre covered to a depth of one centimetre equals 10 litres. That makes the basic calculation straightforward: area in square metres × depth in centimetres × 10.
A 12 m² border covered to 5 cm therefore needs 12 × 5 × 10 = 600 litres before any extra allowance. The calculator then adds the percentage you choose and rounds bag quantities up to a whole bag.
Use the depth that fits the material and the job.
This calculator does not prescribe a universal mulch depth because the right amount depends on the material, whether the area is newly mulched or being topped up, the plants present and the supplier's guidance.
Measure the depth you actually intend to apply and enter that value directly. If an existing mulch layer remains in place, calculate only the additional depth you plan to add rather than the total finished depth.
Use litres for bags and cubic metres for bulk material.
Retail bags are commonly labelled in litres, while bulk landscape materials are often sold by cubic volume. The calculator shows both units so the same measurement can be used when comparing bagged material with a bulk quote.
Because 1,000 litres equals 1 cubic metre, a result of 1,500 litres is 1.50 m³. Bag counts always round upward because a fraction of a bag normally means buying the next full bag.
Real beds are rarely perfect rectangles with perfectly even depth.
An allowance can cover measurement error, small low spots, uneven spreading or settling. The calculator leaves that decision with you instead of silently adding extra material.
Set the allowance to 0% when you want the pure geometric volume. If you use an allowance, the tool shows both the base volume and the final purchase volume so the difference remains transparent.