Topsoil, Compost, Mulch & Bark Calculator

Who this is for

Anyone landscaping a border, raised bed, lawn or planting area and trying to work out how much topsoil, compost, bark or mulch to order — homeowners doing it themselves and tradespeople quoting the materials side of a job.

Should I order extra for settlement?

Yes — loose material compacts once it's down and watered in, and topsoil in particular can settle by 10–20% over the following weeks. Many people round their order up, or plan to top up once it's bedded in, rather than buying it all as a single one-off.

Why does the tonnes figure change with the material?

Because different materials pack to very different densities for the same volume — a cubic metre of topsoil weighs roughly four times as much as the same volume of bark. The density figures here are approximate; actual weight depends on moisture content and the specific supplier's mix, so treat the tonnes figure as an estimate, not a delivery-note guarantee.

How big is a bulk bag really?

This calculator assumes roughly 0.72 m³ per bulk bag (a common "jumbo bag" size), but suppliers vary — some sell bags closer to 0.8 m³, others less. Always check the specific bag size quoted by whoever you're ordering from before relying on the bag count here.

What if my area isn't a simple rectangle?

Split it into rectangles (or roughly rectangular sections), work out each one separately, and add the volumes together — or switch to "enter area directly" and use the total square metres from however you've measured it.

I'm prepping a new lawn — what else do I need to work out?

Once you've got a topsoil bed depth and volume sorted here, the next question is usually how much turf goes on top. Our Turf Calculator takes your lawn area and wastage allowance and works out the rolls to order, and it has its own quick topsoil-depth estimate built in too if you just want a rough figure without switching tools.

Need hard standing instead of a planted area?

If part of the job is a path, driveway or patio sub-base rather than topsoil for planting, see our Gravel & Aggregate Calculator for MOT Type 1, decorative gravel or slate in tonnes and bulk bags.