Formulas
Fire Flow Formula
NFF
A fire flow formula estimates how much water a building needs to control a fire, from its size and the area involved. Pre-planning methods like the national-academy and Iowa approaches give a target flow before crews arrive.
These are planning estimates, not precise numbers. One common method scales the flow from the building's floor area and the fraction involved; another keys off the volume of the space. Both translate a structure into an approximate gallons-per-minute goal.
Knowing the needed fire flow shapes the whole supply plan: how big a line, how many lines, and whether a single hydrant can carry it or the operation needs a relay or a shuttle. It is where size-up meets water supply.
Where this shows up
Calculator
Fire Flow (NFA & Iowa)