Enter the length, width, and height of an area of a building that is on fire into the calculator to determine the required fire flow.

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## Fire Flow Formula

The following two formulas are the two most common formulas used to calculate fire flow.

RFF = V / 100 (ISU Method)

RFF = L*W / 3 (NFA Method)

- Where RFF is the required fire flow (GPM)
- V is the volume (square feet)
- L is the length (feet)
- W is the width

To calculate fire flow, multiply the length by the width, then divide by 3.

## Fire Flow Definition

**What is fire flow? **Fire flow is a measure of the total rate of water flow required to suppress a fire. Fire flow is most often expressed in gallons per minute. It’s often used as a rough estimate as opposed to an exact measure.

## Example Problem

How to calculate fire flow?

**First, determine the length of the area on fire.**For this example, the length is 10 ft.

**Next, determine the width of the area.**For this example, the width is 20 ft.

**Next, determine the height.**In this problem the height is 8 ft.

**Finally, calculate the fire flow.**Using the formula: 10*20*8/3 = 16 GPM