Soil, mulch and gravel calculator

The formula, in plain words

1. 1Area: length × width for a rectangle, π × (diameter ÷ 2)² for a circle. Add every bed.
2. 2Cubic metres = area × depth (mm ÷ 1000), plus the material's allowance: about 10% for soils, compost and mulch to settle, and ÷ 0.9 for road base to compact.
3. 3Order = rounded up to the half cubic metre, the way landscape yards sell bulk.
4. 4Tonnes = m³ × the material's density. Bags = litres ÷ bag size for soil and mulch, tonnes ÷ 20 kg for stone and sand.
5. 5Trailer loads: a 6 × 4 trailer takes about 0.5 m³ of soil, sand or gravel, or 0.75 m³ of mulch.

Worked example

A 6 × 1.5 m garden bed: 100 mm of garden mix topped with 75 mm of mulch.

1. 1.Area: 6 × 1.5 = 9 m².
2. 2.Garden mix: 9 × 0.1 = 0.9 m³, + 10% = 0.99 m³, so order 1 m³ (about 0.8 t, two trailer loads).
3. 3.Mulch: 9 × 0.075 = 0.675 m³, + 10% = 0.74 m³, so order 1 m³ (one trailer load).

Answer: 1 m³ of garden mix and 1 m³ of mulch.

How to measure it

• Measure each bed or area: length and width, or the diameter of a round bed.
• Pick what goes in, bottom layer first, and how deep you want each.
• Odd shapes: split them into rectangles and circles.
• Check the material's density with your yard if you need an exact weight.

Where the numbers come from

Every default in the calculator is a number a supplier or manufacturer publishes. We list the source next to it so you can check.

Frequently asked questions