About this calculator
This calculator turns a list of elements you plan to demolish (a slab, a wall, a stud partition) into a skip/container plan. For each element, give its material type and dimensions; the calculator adds up the solid volume, applies a bulking factor to estimate how much space the broken-up debris will actually take, works out its mass, and tells you how many containers of your chosen size you need — checking both the container's volume limit and its maximum load.
Formula
element volume = length x width x thickness
solid volume (per material) = sum of that material's element volumes
loose volume (per material) = solid volume x bulking factor
mass (per material) = solid volume x density [mass is conserved -- only
volume increases when broken up]
total loose volume = sum over all materials
total mass = sum over all materials
containers by volume = ceil(total loose volume / container volume)
containers by mass = ceil(total mass / container max load)
containers needed = the larger of the two
Worked example
A 4 x 3 m, 150 mm concrete slab and a 5 x 2.5 m, 250 mm brick wall, into 4 m³ containers rated to 10 t each.
concrete: 4 x 3 x 0.15 = 1.8 m³ -> loose 1.8 x 1.3 = 2.34 m³; mass 1.8 x 2400 = 4320 kg
brick: 5 x 2.5 x 0.25 = 3.125 m³ -> loose 3.125 x 1.5 = 4.6875 m³; mass 3.125 x 1800 = 5625 kg
total loose volume = 7.0275 m³; total mass = 9945 kg
containers by volume = ceil(7.0275 / 4) = 2
containers by mass = ceil(9.945 / 10) = 1
containers needed = 2 (limited by volume)
FAQ
Why does mass not change when the material bulks up? Breaking a solid element into rubble increases the air gaps between the pieces, so the same mass now occupies more volume. This calculator keeps mass tied to the original solid volume and density, and applies the bulking factor only to the volume figure used for sizing containers.
Which figure decides the container count — volume or mass? Whichever needs more containers. A container can be full by volume before it reaches its weight limit (light, bulky debris like broken drywall), or reach its weight limit while still visually empty (dense debris like concrete or brick) — the calculator checks both and reports the binding one.
Where do the bulking factors and densities come from? They are editable estimates, not measured values for your specific debris — see Assumptions below. Adjust them if your waste contractor or skip-hire company gives you more specific figures for your material and condition.
Which standard does this follow? None is cited. Bulking factors and debris densities are published by waste-management and skip-hire companies for planning purposes, not defined in a single technical standard.
Assumptions and limits
Every material's bulking factor and bulk density are user inputs with example defaults — not measured data for your specific debris, which varies with how it was broken up, its moisture content, and what is mixed in with it. Dimensions are entered per element as length x width x thickness; if you already know an element's volume directly, enter equivalent dimensions (e.g. 1 x 1 m x the known volume in metres) rather than the real shape. No drawing is produced — this calculator's result is a materials/logistics list.