Fire pump discharge pressure calculator
Enter your nozzle, hose, flow, and elevation to get pump discharge pressure (PDP) and friction loss instantly — using the same validated NFPA 1002 / IFSTA hydraulics that power the PumpForge simulator.
PDP = nozzle pressure + friction loss + elevation + appliance loss. This tool runs the identical hydraulics engine as the PumpForge training simulator — identical inputs always produce identical outputs.
How pump discharge pressure is calculated
Pump discharge pressure (PDP) is the pressure the pump operator must produce so the nozzle receives its rated pressure at the end of the line. It is the sum of four parts:
Where NP is nozzle pressure, FL is friction loss, EL is elevation pressure, and AL is appliance loss. Friction loss is the big variable — it grows with the square of the flow rate:
C is the hose coefficient, Q is flow in gpm, and L is hose length in feet. Elevation adds 0.434 psi per foot of gain (about 5 psi per floor); going below the pump subtracts the same.
Hose friction-loss coefficients
| Hose diameter | Coefficient (C) |
|---|---|
| 1¾″ | 15.5 |
| 2″ | 8.0 |
| 2½″ | 2.0 |
| 3″ | 0.80 |
| 4″ | 0.20 |
| 5″ | 0.08 |
Common nozzle pressures
| Nozzle | Pressure |
|---|---|
| Smooth bore handline | 50 psi |
| Smooth bore master stream | 80 psi |
| Low-pressure fog | 75 psi |
| Fog / combination | 100 psi |
Worked example
A 2½″ line, 200 ft long, flowing 250 gpm to a smooth bore handline (50 psi nozzle pressure), no elevation:
= 2.0 × 6.25 × 2 = 25 psi
PDP = 50 + 25 + 0 + 0 = 75 psi
Frequently asked questions
- What is pump discharge pressure (PDP)?
- The total pressure the operator produces at the discharge so the nozzle gets its rated pressure. PDP = nozzle pressure + friction loss + elevation + appliance loss.
- How do you calculate friction loss?
- FL = C × (Q/100)² × (L/100). Flow has the biggest effect because it is squared — doubling the gpm quadruples the friction loss.
- How much does elevation change the pressure?
- About 0.434 psi per foot of height (roughly 5 psi per floor). Add it going up, subtract it going down.
- Are these the standard fire-service coefficients?
- Yes — these are the IFSTA / National Fire Academy hose coefficients, the same ones used in NFPA 1002 Chapter 5 training.
Coefficients per IFSTA / NFA. For training and estimation; always verify against your department SOPs and nozzle manufacturer ratings. See how the hydraulics engine works or browse the 22 built-in scenarios. Related tools: friction loss calculator, nozzle reaction calculator, and smooth bore flow calculator. These calculations are core skills under NFPA 1002. Sizing the attack? Estimate demand with the required fire flow calculator or the fire flow chart.
The scenario: 200 ft of 1¾" hose flowing 150 GPM through a 100 PSI fog nozzle, to a crew two floors up.
Friction loss: FL = C × (Q/100)² × (L/100) = 15.5 × (1.5)² × 2 ≈ 70 PSI. Elevation: 2 floors × 5 PSI = 10 PSI.
PDP = NP + FL + EP = 100 + 70 + 10 = 180 PSI.
Punch the same numbers into the calculator above and you'll get the same answer — then change one variable at a time (drop to 95 GPM, swap to 2½" hose) and watch which term moves. That's the intuition the fireground requires.
Calculating it on paper is one thing. Doing it under pressure is another.
PumpForge puts your operators on a realistic pump panel running these exact hydraulics at 20 Hz — across 22 built-in scenarios, with automatic scoring and after-action reports. Every station, any computer or tablet.