Motor Horsepower to Pump Output Calculator
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Motor Horsepower to Pump Output Calculator
Calculate pump output flow rate (GPM) and hydraulic power from motor horsepower, pump efficiency, and system pressure.
Motor Horsepower (HP)
Pump Efficiency (%)
System Pressure (PSI)
Fluid Specific Gravity (SG)
Calculate
Results will appear here.
function motCalc() { var resultDiv = document.getElementById('mot-result');
var hp = parseFloat(document.getElementById('mot-hp').value); var eff = parseFloat(document.getElementById('mot-eff').value); var psi = parseFloat(document.getElementById('mot-psi').value); var sg = parseFloat(document.getElementById('mot-sg').value);
// --- Validation --- if (isNaN(hp) || hp ⚠ Please enter a valid Motor Horsepower greater than 0.'; return; } if (isNaN(eff) || eff 100) { resultDiv.innerHTML = '⚠ Please enter a valid Pump Efficiency between 0.1% and 100%.'; return; } if (isNaN(psi) || psi ⚠ Please enter a valid System Pressure greater than 0 PSI.'; return; } if (isNaN(sg) || sg ⚠ Please enter a valid Specific Gravity greater than 0.'; return; }
var effDecimal = eff / 100.0;
// --- Core Formulas --- // Hydraulic Horsepower (WHP) = Motor HP × Efficiency var whp = hp * effDecimal;
// Flow Rate (GPM) = (HP × 1714 × Efficiency) / (PSI × SG) // Derivation: 1 HP = 1714 GPM·PSI (unit constant) var gpm = (hp * 1714.0 * effDecimal) / (psi * sg);
// Flow Rate in m³/h (1 GPM = 0.227125 m3/h) var m3h = gpm * 0.227125;
// Flow Rate in L/min (1 GPM = 3.78541 L/min) var lpm = gpm * 3.78541;
// Hydraulic Power in Watts (1 HP = 745.7 W) var watts = whp * 745.7;
// Torque at pump shaft (ft·lbf) — requires RPM; show note if not provided // Torque (ft·lbf) = (HP × 5252) / RPM — informational formula shown in formula section
// --- Output --- resultDiv.innerHTML = 'Results:' + '' + 'Hydraulic (Water) Horsepower' + '' + whp.toFixed(4) + ' HP (WHP)' + 'Pump Output Flow Rate' + '' + gpm.toFixed(4) + ' GPM' + 'Flow Rate (Metric)' + '' + m3h.toFixed(4) + ' m³/h | ' + lpm.toFixed(4) + ' L/min' + 'Hydraulic Power Output' + '' + watts.toFixed(2) + ' W (' + (watts/1000).toFixed(4) + ' kW)' + 'Power Lost to Inefficiency' + '' + ((hp - whp) * 745.7).toFixed(2) + ' W (' + (hp - whp).toFixed(4) + ' HP)' + ''; }
#### Formulas Used
1. Hydraulic (Water) Horsepower (WHP):
WHP = Motor HP × (Efficiency / 100)
2. Pump Output Flow Rate (GPM):
GPM = (HP × 1714 × Efficiency) / (PSI × SG)
Where: 1 HP = 1714 GPM·PSI (unit conversion constant derived from 1 HP = 550 ft·lbf/s and 1 gallon = 231 in³)
3. Hydraulic Power (Watts):
Power (W) = WHP × 745.7
4. Pump Shaft Torque (informational, requires RPM):
Torque (ft·lbf) = (HP × 5252) / RPM
#### Assumptions & References
- The unit constant 1714 is derived from: 1 HP = 550 ft·lbf/s; 1 PSI = 144 lbf/ft²; 1 US gallon = 231 in³ → GPM = (HP × 33,000) / (PSI × 0.4335 × 8.34 × SG) ≈ HP × 1714 / (PSI × SG).
- Specific Gravity defaults to 1.0 (fresh water at ~60°F / 15.6°C). Adjust for other fluids (e.g., seawater ≈ 1.025, diesel ≈ 0.85).
- Typical centrifugal pump efficiencies range from 50% to 90%; positive displacement pumps can reach 85–95%.
- References: Hydraulic Institute Standards; Karassik et al., Pump Handbook, 4th Ed.; Crane Co. Technical Paper 410.
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