Compost Bin Volume Calculator

About this calculator

A compost bin's usable capacity is its geometric volume — length × width × height for a rectangular bin, or the cylinder formula for a round one — multiplied by how full you intend to fill it, since compost needs headspace for turning and aeration. Converting that volume to a weight requires the bulk density of the material being composted, which typically runs around 500–700 kg per cubic meter for active, part-decomposed compost, though fresh green waste and finished compost differ noticeably.

Home gardeners and allotment growers use this calculation when choosing a bin size for their household's food and garden waste output, or when working out how much finished compost a given bin will yield for spreading on beds. Undersizing a bin means waste piles up faster than it breaks down; oversizing it wastes space and can slow decomposition if the pile never builds enough mass to heat properly.

This calculator takes your bin dimensions, fill level and material density, and returns the bin's volume and how much material it can hold.