Fire Flow Calculator
Calculate required fire flow in GPM using NFA and Iowa methods for fire suppression planning.
What Is a Fire Flow Calculator?
A fire flow calculator estimates required water flow in gallons per minute (GPM) to suppress a building fire. Firefighters and engineers use it for hydrant planning, pump sizing, and resource staging before an incident.
NFA Fire Flow Formula
$$ \text{RFF} = \frac{L \times W}{3} \times F $$
Where $L$ and $W$ are building length and width in feet, and $F$ is the number of floors on fire. Adjust for partial involvement (percentage of building burning) and interior or exterior exposures, each adding 25% per exposed object.
Iowa Fire Flow Formula
$$ \text{RFF} = \frac{L \times W \times H}{100} $$
Where $H$ is building height in feet. This method uses total fire volume rather than floor count. Results are planning estimates; actual needs depend on fuel load, wind, and construction type.
Frequently Asked Questions
What is required fire flow (RFF)?
RFF is the water flow rate in GPM needed to control or extinguish a fire. It guides how many hydrants, hoses, and pumpers to deploy at a scene.
What GPM does a fire hydrant provide?
Typical municipal hydrants deliver 500 to 1,500 GPM depending on water main size, pressure, and local standards. Always verify with flow testing.
What is the maximum fire flow?
Many planning guides cap a single fire event at about 12,000 GPM (45,500 L/min). Larger fires may need multiple water sources.
How do I calculate fire flow for a 20 by 20 foot building?
Using the NFA formula with one floor: RFF = (20 × 20) / 3 ≈ 133 GPM. Add exposure and involvement adjustments as needed.
NFA vs Iowa method: which should I use?
Use the method your department or jurisdiction specifies. NFA is common for floor-based estimates. Iowa uses building volume and works well when height matters.
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