Site maths
Packs, units & waste
- where
- target units
- net units
- waste (%)
- packs
- units per pack
Explain this equation
This converts a net number of units into whole supplier packs, after adding waste, and shows how many spares you end up with.
N is the net number of units. w is the waste percentage. T is the target number of units including waste. s is the number of units in one pack and P is the number of packs. The calculator also gives the units supplied and the surplus above the target.
N × (1 + w/100) adds the waste and is rounded up to a whole unit. That is divided by the pack size and rounded up again, because you can only buy full packs. The ⌈ ⌉ brackets mean round up.
1000 bricks with 5% waste is 1050. At 500 to a pack that is 3 packs, 1500 bricks, leaving 450 spare. Sometimes a split pack is worth asking for.
Watch out: waste is added before rounding to packs, so the surplus is on top of the waste allowance.
Convert a net quantity to whole supplier packs.
Enter your values to see the result.
Good to know
Rounding to packs happens after waste allowance. Pack size is supplier-specific.
Sources
- Geometry / arithmetic
Estimates are not design approval or British Standards compliance checks. Structural arch, retaining-wall, wind, foundation, lintel and masonry-capacity design are not performed. Use the project engineer’s specification.