FireOps CalcFL per 100 ft = C × (GPM ÷ 100)²
Total FL = FL per 100 ft × (hose length ÷ 100)
Step-by-step process
Find the flowUse the target GPM for the line.
Convert GPM to QDivide GPM by 100.
Square QMultiply Q by itself.
Multiply by the C-valueUse the hose coefficient for the selected hose.
Multiply by hose lengthMultiply the per-100-ft loss by the number of 100-ft sections.
Worked example
Flow185 GPM
Q1.85
C-value15.5
FL per 100 ftabout 53 PSI
Total for 200 ftabout 106 PSI
This is why doubling flow can dramatically increase friction loss. Flow changes matter more than many new pump operators expect.
Common mistakes to avoid
- Using a default nozzle pressure that does not match the actual nozzle.
- Forgetting extra hose, elevation, or appliance loss.
- Using textbook coefficients when your department has known hose data.
- Treating a training estimate as a replacement for department SOPs or instructor direction.
How FireOps Calc helps
FireOps Calc is built to make this process faster on a phone. Open the web calculator, enter your hose, nozzle, flow, elevation, and appliance values, then review the math breakdown instead of only seeing a final number.
FAQ
Why does GPM affect friction loss so much?
Because the flow term is squared. A modest increase in flow can create a much larger increase in friction loss.
Should I use exact C-values?
Use your department hose data when available. Older, newer, low-friction, and custom hose can all behave differently.