.calc-container-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.calculator-box {
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calculator-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.input-group {
margin-bottom: 20px;
}
.input-label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #495057;
}
.form-control {
width: 100%;
padding: 12px;
font-size: 16px;
border: 1px solid #ced4da;
border-radius: 4px;
box-sizing: border-box;
transition: border-color 0.15s ease-in-out;
}
.form-control:focus {
border-color: #007bff;
outline: none;
}
.select-control {
background-color: white;
cursor: pointer;
}
.calc-btn {
display: block;
width: 100%;
padding: 14px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: 600;
cursor: pointer;
transition: background-color 0.2s;
margin-top: 20px;
}
.calc-btn:hover {
background-color: #0056b3;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #e8f5e9;
border: 1px solid #c8e6c9;
border-radius: 4px;
text-align: center;
display: none;
}
.result-label {
font-size: 14px;
color: #2e7d32;
text-transform: uppercase;
letter-spacing: 1px;
margin-bottom: 5px;
}
.result-value {
font-size: 32px;
font-weight: 700;
color: #1b5e20;
}
.article-content h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.article-content p {
margin-bottom: 15px;
}
.article-content ul {
margin-bottom: 15px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 8px;
}
.formula-box {
background: #fff3cd;
padding: 15px;
border-left: 5px solid #ffc107;
font-family: monospace;
margin: 20px 0;
font-size: 1.1em;
}
function calculateSpeed() {
// Retrieve inputs
var rpm = parseFloat(document.getElementById('rpm_input').value);
var diameter = parseFloat(document.getElementById('diameter_input').value);
var unit = document.getElementById('unit_select').value;
var resultContainer = document.getElementById('result_container');
var fpmOutput = document.getElementById('fpm_output');
var mphOutput = document.getElementById('mph_output');
// Validation
if (isNaN(rpm) || isNaN(diameter) || rpm < 0 || diameter < 0) {
alert("Please enter valid positive numbers for RPM and Diameter.");
resultContainer.style.display = "none";
return;
}
// Constants
var PI = Math.PI;
var fpm = 0;
// Calculation Logic
// Formula: FPM = RPM * Circumference (in feet)
if (unit === 'inches') {
// If diameter is inches, divide by 12 to get feet
// FPM = (RPM * Diameter * PI) / 12
fpm = (rpm * diameter * PI) / 12;
} else if (unit === 'feet') {
// If diameter is feet, no conversion needed for length
// FPM = RPM * Diameter * PI
fpm = rpm * diameter * PI;
} else if (unit === 'mm') {
// If diameter is mm, convert to inches (/25.4) then to feet (/12)
// Or directly to feet: 1 ft = 304.8 mm
fpm = (rpm * diameter * PI) / 304.8;
}
// Secondary calculation for Miles Per Hour (MPH) for context
// 1 MPH = 88 FPM
var mph = fpm / 88;
// Display Results
resultContainer.style.display = "block";
fpmOutput.innerHTML = fpm.toFixed(2) + " ft/min";
mphOutput.innerHTML = "(" + mph.toFixed(2) + " mph)";
}
Understanding RPM to Feet Per Minute (FPM) Conversion
Converting Revolutions Per Minute (RPM) to Feet Per Minute (FPM) is a critical calculation in manufacturing, machining, and material handling. While RPM measures how fast an object rotates around an axis, FPM (often referred to as Surface Feet Per Minute or SFM) measures the linear distance a point on the rotating surface travels in one minute.
This metric is essential for configuring conveyor belt speeds, determining cutting speeds on lathes or mills, and calibrating web press machinery.
The RPM to FPM Formula
The conversion relies on finding the circumference of the rotating object (roller, wheel, or cutting tool) and multiplying it by the rotational speed.
FPM = (RPM × Diameter × π) / 12
Where:
- RPM: The rotational speed of the motor or shaft.
- Diameter: The diameter of the roller or wheel (measured in inches).
- π (Pi): Approximately 3.14159.
- 12: The conversion factor to turn inches into feet.
If your diameter is already measured in feet, the formula simplifies to:
FPM = RPM × Diameter (ft) × π
Practical Examples
Example 1: Conveyor Belt System
Imagine a conveyor belt driven by a head pulley with a diameter of 10 inches. The motor is running at 175 RPM. To find the linear speed of the belt:
- Circumference = 10 inches × 3.14159 = 31.4159 inches
- Convert to feet: 31.4159 / 12 = 2.618 feet per revolution
- Total Speed = 175 RPM × 2.618 ft = 458.15 FPM
Example 2: Machining (Lathe Work)
A machinist is turning a steel shaft with a diameter of 2 inches. The chuck is spinning at 1200 RPM. The surface feet per minute (cutting speed) is:
- Calculation: (1200 × 2 × 3.14159) / 12
- Result: 628.32 FPM (or SFM)
Why FPM Matters
Safety limits: Tires, saw blades, and grinding wheels have maximum rated surface speeds. Exceeding the FPM limit, even if the RPM seems low on a large wheel, can lead to catastrophic failure.
Process Control: In coating or printing applications, the web speed (FPM) determines drying time and coating thickness. Accurate conversion from motor RPM ensures product quality.
Tool Life: In CNC machining, running a tool at the correct Surface Feet Per Minute maximizes tool longevity and finish quality. Different materials (Aluminum vs. Steel) require specific FPM rates regardless of the tool diameter.
Frequently Asked Questions
Does the shaft size affect FPM?
No, the FPM is determined by the outside diameter of the object contacting the material or environment (like the conveyor roller surface or tire tread), not the internal drive shaft size.
How do I convert FPM back to RPM?
If you know your target linear speed and need to set the motor speed, rearrange the formula: RPM = (FPM × 12) / (Diameter × π).