How the calculation works
The formulas
Use average thickness for a rectangular floor. Convert millimetres to metres before multiplying by area. Whole bags round upward after applying the entered order allowance.
Volume = length × width × thickness
Order volume = volume × (1 + allowance/100)
Bags = ceil(order volume ÷ mixed yield per bag)
Assumptions to check
- Uniform average thickness is assumed; falls or irregular areas require separate element estimates.
- This does not specify mixes, curing, reinforcement, or installation thickness limits.
A worked example
5 × 4 m at 50 mm is 1 m³. With 5% allowance and 12.5 L per bag, buy 84 bags.