How to use the mulch, soil and gravel calculator
- Choose the material. It changes the default bag size, the example prices and the weight estimate.
- Measure the length and width of the bed, lawn area or path. Split curved beds into rough rectangles and run each one.
- Enter the depth you want once the material has settled.
- Check the bag size on the bags you plan to buy, and add bag and bulk prices.
- Compare the two costs, remembering that bulk deliveries usually carry a delivery charge.
How the volume is worked out
Bags = volume ÷ bag size, rounded up
Weight ≈ volume × typical density
One cubic yard covers 324 sq ft at 1 in deep, or 108 sq ft at 3 in. The densities used for the weight are typical loose figures: about 0.3 t/m³ for mulch, 1.25 for topsoil and 1.6 for gravel and sand. Wet material is heavier, so treat the weight as a guide for choosing a trailer or a delivery, not a weighbridge figure.
Worked example
A 20 × 10 ft garden bed covered with 3 in of mulch, 10% extra for settling, 2 cu ft bags at $4.50 or bulk mulch at $40 per cubic yard:
- Volume: 20 × 10 × (3 ÷ 12) = 50 cu ft, plus 10% = 55 cu ft, which is 2.04 cu yd of mulch.
- Bags: 55 ÷ 2 = 27.5, so 28 × 2 cu ft bags, costing $126.00.
- Bulk: $81.48 before delivery, so the cheaper option is Bulk delivery.
- Mulch is light, at roughly 0.3 tonnes per cubic metre, so the load weighs about 0.52 tons.
Tips and common mistakes
- Mulch depth: 2 to 3 in (5 to 7.5 cm) is usual for beds. Keep mulch a few inches away from tree trunks and plant stems so they do not stay wet and rot.
- Topsoil settles. Fresh topsoil compacts as it settles, so order a little more than the finished depth and firm it as you spread.
- Gravel needs a base. Paths and driveways last longer with a compacted base and landscape fabric underneath; the depth here is the top layer only.
- Check access for bulk. A delivery truck needs space to tip. Put a tarp down and plan the barrow route before it arrives.
US, UK and Canada differences
US garden centres sell mulch in 2 or 3 cu ft bags and bulk by the cubic yard, while stone and sand are often sold by the ton. In the UK, bagged products are labelled in litres, and loose materials come in bulk bags (often called dumpy bags) that hold around three-quarters of a cubic metre to a tonne. Canadian suppliers usually sell bulk by the cubic yard or cubic metre, so check which unit a quote uses.
Metric units and other countries
In metric mode, depth is in centimetres, volume in cubic metres and bags in litres, and the weight is given in tonnes. Where sand and crushed stone are sold by the truck or trolley load, ask the supplier how many cubic metres a load holds, then compare it with the volume here. Type your local prices.