Pump Flow Rate Calculator Online

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Pump Flow Rate Calculator

Calculate GPM, LPM, and m³/h based on volume or pipe dimensions

Gallons (US) Liters Cubic Meters (m³)
Minutes Seconds Hours

Calculated Results:

US GPM
0.00
Liters/Min
0.00
m³/Hour
0.00

Understanding Pump Flow Rate Calculations

A pump's flow rate is a critical metric used to determine how much fluid a pump can move within a specific timeframe. Whether you are sizing a hydraulic system, a pool pump, or an industrial chemical feed system, understanding the flow rate (measured typically in Gallons Per Minute – GPM) ensures the efficiency and longevity of your equipment.

Method 1: Volume and Time Formula

This is the most direct way to measure flow rate. If you know how much fluid was moved and how long it took, the formula is:

Flow Rate (Q) = Volume (V) / Time (t)

To convert this to standard GPM (US Gallons Per Minute):

  • If volume is in Gallons and time in Minutes, Q = V / t.
  • If volume is in Liters, multiply by 0.264 to get Gallons.

Method 2: Pipe Diameter and Velocity

In many engineering scenarios, you know the size of the pipe and the speed (velocity) at which the fluid is traveling. The flow rate can be determined using the cross-sectional area of the pipe:

Q = A × v

Where A is the Area (π × radius²) and v is Velocity. For quick calculation using inches and feet per second:

GPM = (Velocity in ft/s × Diameter in inches²) / 0.4085

Practical Example

If you have a 2-inch pipe and the fluid is moving at 5 feet per second:

  1. Square the diameter: 2² = 4.
  2. Multiply by velocity: 4 × 5 = 20.
  3. Divide by the constant 0.4085.
  4. Result: Approximately 48.96 GPM.

Note: This calculator assumes a full pipe and steady-state flow. For viscous fluids like heavy oils, additional friction loss factors may apply.

function calculateFlowByVol() { var vol = parseFloat(document.getElementById('totalVolume').value); var vUnit = document.getElementById('volumeUnit').value; var time = parseFloat(document.getElementById('totalTime').value); var tUnit = document.getElementById('timeUnit').value; if (isNaN(vol) || isNaN(time) || time <= 0) { alert("Please enter valid positive numbers for volume and time."); return; } var volInGallons = 0; if (vUnit === 'gallons') { volInGallons = vol; } else if (vUnit === 'liters') { volInGallons = vol * 0.264172; } else if (vUnit === 'cubicmeters') { volInGallons = vol * 264.172; } var timeInMinutes = 0; if (tUnit === 'minutes') { timeInMinutes = time; } else if (tUnit === 'seconds') { timeInMinutes = time / 60; } else if (tUnit === 'hours') { timeInMinutes = time * 60; } var gpm = volInGallons / timeInMinutes; displayResults(gpm); } function calculateFlowByVel() { var dia = parseFloat(document.getElementById('pipeDiameter').value); var vel = parseFloat(document.getElementById('flowVelocity').value); if (isNaN(dia) || isNaN(vel) || dia <= 0) { alert("Please enter valid positive numbers for diameter and velocity."); return; } // Formula: GPM = (Velocity (ft/s) * Diameter(in)^2) / 0.4085 var gpm = (vel * Math.pow(dia, 2)) / 0.4085; displayResults(gpm); } function displayResults(gpmValue) { var lpm = gpmValue * 3.78541; var m3h = gpmValue * 0.227125; document.getElementById('resGPM').innerHTML = gpmValue.toFixed(2); document.getElementById('resLPM').innerHTML = lpm.toFixed(2); document.getElementById('resM3H').innerHTML = m3h.toFixed(2); document.getElementById('resultDisplay').style.display = 'block'; }

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