body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 800px;
margin: 0 auto;
padding: 20px;
}
.calculator-container {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-header {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
}
.input-group {
margin-bottom: 20px;
}
.input-row {
display: flex;
gap: 15px;
align-items: flex-end;
}
.input-wrapper {
flex: 1;
}
label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #495057;
}
input[type="number"], select {
width: 100%;
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
input[type="number"]:focus, select:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 0 2px rgba(0,123,255,0.25);
}
.calc-btn {
width: 100%;
background-color: #007bff;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #0056b3;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #ffffff;
border: 1px solid #dee2e6;
border-left: 5px solid #28a745;
border-radius: 4px;
display: none;
}
.result-header {
font-size: 18px;
font-weight: bold;
color: #28a745;
margin-bottom: 15px;
border-bottom: 1px solid #eee;
padding-bottom: 10px;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
font-size: 16px;
}
.result-label {
color: #666;
}
.result-value {
font-weight: bold;
color: #212529;
}
.article-content {
background: #fff;
padding: 20px 0;
}
h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 30px;
}
h3 {
color: #34495e;
margin-top: 25px;
}
ul {
padding-left: 20px;
}
li {
margin-bottom: 10px;
}
.formula-box {
background: #eef2f7;
padding: 15px;
border-left: 4px solid #007bff;
font-family: "Courier New", Courier, monospace;
margin: 20px 0;
}
@media (max-width: 600px) {
.input-row {
flex-direction: column;
gap: 15px;
}
}
How to Calculate Pipe Diameter from Flow Rate
Determining the correct pipe size is a fundamental task in fluid mechanics and engineering. Using the wrong diameter can lead to excessive pressure drops, noise, system erosion (if velocity is too high), or sedimentation and unnecessarily high material costs (if velocity is too low).
This guide explains the physics behind the calculation and provides the formulas used by the calculator above.
The Fundamental Formula
The relationship between pipe diameter, flow rate, and velocity is derived from the continuity equation for incompressible fluids:
Q = A × v
Where:
- Q = Volumetric Flow Rate (e.g., m³/s)
- A = Cross-Sectional Area of the pipe (m²)
- v = Velocity of the fluid (m/s)
Solving for Diameter
Since the cross-sectional area of a round pipe is calculated as A = π × (d/2)² or A = (π × d²) / 4, we can substitute this into the continuity equation and rearrange it to solve for the diameter (d):
d = √ [ (4 × Q) / (π × v) ]
Step-by-Step Calculation Example
Let's calculate the required pipe diameter for a water pump system with the following specifications:
- Flow Rate: 50 cubic meters per hour (m³/h)
- Target Velocity: 2 meters per second (m/s)
Step 1: Convert Flow Rate to Standard Units
First, we must ensure the time units match. Since velocity is in seconds, convert the flow rate from hours to seconds.
50 m³/h ÷ 3600 seconds = 0.01389 m³/s
Step 2: Apply the Formula
Now, plug the values into the diameter formula:
d = √ [ (4 × 0.01389) / (3.14159 × 2) ]
d = √ [ 0.05556 / 6.28318 ]
d = √ [ 0.00884 ]
d ≈ 0.094 meters
Step 3: Convert to Practical Units
To make this useful, convert meters to millimeters or inches:
- Millimeters: 0.094 m × 1000 = 94 mm
- Inches: 94 mm ÷ 25.4 ≈ 3.7 inches
In this scenario, a standard 4-inch (DN100) pipe would likely be selected to maintain the velocity below the 2 m/s target.
Typical Velocity Guidelines
When designing a system, selecting the right velocity is crucial. Here are common industry standards for water:
- Pump Suction: 0.6 to 1.5 m/s (2 to 5 ft/s) – kept low to prevent cavitation.
- Pump Discharge: 1.5 to 3.0 m/s (5 to 10 ft/s) – efficient transport.
- Drain Lines: Varies, but usually sufficient to ensure self-cleaning.
function calculatePipeDiameter() {
// 1. Get Input Values
var flowRateInput = document.getElementById('flowRate').value;
var flowUnit = document.getElementById('flowUnit').value;
var velocityInput = document.getElementById('velocity').value;
var velocityUnit = document.getElementById('velocityUnit').value;
// 2. Validate Inputs
if (flowRateInput === "" || velocityInput === "" || isNaN(flowRateInput) || isNaN(velocityInput)) {
alert("Please enter valid numbers for both Flow Rate and Velocity.");
return;
}
var Q_val = parseFloat(flowRateInput);
var v_val = parseFloat(velocityInput);
if (Q_val <= 0 || v_val A = Q / v
var area_m2 = Q_SI / v_SI;
// A = (pi * d^2) / 4 => d = sqrt(4 * A / pi)
var diameter_m = Math.sqrt((4 * area_m2) / Math.PI);
// 5. Convert Results for Display
var diameter_mm = diameter_m * 1000;
var diameter_inch = diameter_mm / 25.4;
// Format Cross Sectional Area (cm2 for readability)
var area_cm2 = area_m2 * 10000;
// 6. Display Results
document.getElementById('resMM').innerHTML = diameter_mm.toFixed(2) + " mm";
document.getElementById('resInches').innerHTML = diameter_inch.toFixed(2) + " inches";
document.getElementById('resArea').innerHTML = area_cm2.toFixed(2) + " cm²";
// Show result box
document.getElementById('resultBox').style.display = "block";
}