Calculate volumetric flow rate based on pipe diameter and fluid velocity.
Millimeters (mm)
Inches (in)
Meters per second (m/s)
Feet per second (ft/s)
Calculation Results:
Liters per Minute (LPM):0
Cubic Meters per Hour (m³/h):0
US Gallons per Minute (GPM):0
How to Calculate Pump Flow Rate
The pump flow rate is the volume of fluid that passes through a specific point in a system per unit of time. Understanding the flow rate is critical for sizing pumps, choosing pipe diameters, and ensuring the efficiency of hydraulic systems.
The Flow Rate Formula
The most common way to calculate flow rate ($Q$) when you know the pipe size and fluid speed is using the Area-Velocity equation:
Q = A × v
Where:
Q: Volumetric Flow Rate
A: Cross-sectional Area of the pipe ($\pi \times r^2$)
v: Velocity of the fluid
Step-by-Step Calculation Guide
Determine Pipe Diameter: Measure the internal diameter of the pipe. If the pipe is 2 inches, convert that to meters (0.0508 m) for standard SI calculations.
Calculate Cross-sectional Area: Use the formula $A = \pi \times (Diameter / 2)^2$.
Measure Velocity: Determine how fast the fluid is moving (e.g., 2 meters per second).
Multiply: Multiply the area by the velocity to get the flow rate in cubic meters per second ($m^3/s$).
Convert Units: Convert $m^3/s$ to more common units like Gallons per Minute (GPM) or Liters per Minute (LPM).
Practical Example
Imagine a pump pushing water through a pipe with an internal diameter of 100mm (0.1m) at a velocity of 2 meters per second.
Area = $3.14159 \times (0.05)^2 = 0.007854 m^2$
Flow Rate = $0.007854 \times 2 = 0.015708 m^3/s$
Converting to LPM: $0.015708 \times 60,000 = 942.48$ Liters per Minute.
Why Flow Rate Matters
If the flow rate is too high, you risk "cavitation" or excessive friction loss which can damage the pipe and pump. If the flow rate is too low, the system may not deliver enough fluid to perform the required work, such as cooling a machine or providing enough pressure for a sprinkler system.
function calculatePumpFlow() {
var diameter = parseFloat(document.getElementById("pipeDiameter").value);
var dUnit = document.getElementById("diameterUnit").value;
var velocity = parseFloat(document.getElementById("flowVelocity").value);
var vUnit = document.getElementById("velocityUnit").value;
if (isNaN(diameter) || isNaN(velocity) || diameter <= 0 || velocity <= 0) {
alert("Please enter valid positive numbers for diameter and velocity.");
return;
}
var diameterMeters;
if (dUnit === "mm") {
diameterMeters = diameter / 1000;
} else {
diameterMeters = diameter * 0.0254;
}
var velocityMS;
if (vUnit === "ms") {
velocityMS = velocity;
} else {
velocityMS = velocity * 0.3048;
}
var radius = diameterMeters / 2;
var area = Math.PI * Math.pow(radius, 2);
// Q in m3/s
var qM3S = area * velocityMS;
// Conversions
var qLPM = qM3S * 60000;
var qM3H = qM3S * 3600;
var qGPM = qM3S * 15850.3231;
document.getElementById("resLPM").innerText = qLPM.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("resM3H").innerText = qM3H.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("resGPM").innerText = qGPM.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("pumpResult").style.display = "block";
}