Maxi Calculator

RPM Calculator

Calculate rotational speed and related measurements

RPM Calculator

Enter the diameter of the rotating object

Enter the surface speed in feet per minute

Table of Contents
What is RPM?

RPM (Revolutions Per Minute) is a measure of rotational speed. Understanding RPM is crucial for:

  • Engine performance measurement
  • Machine tool operation
  • Fan and pump speed control
  • Industrial equipment maintenance
  • Vehicle diagnostics

Related measurements include:

  • Surface Speed: Linear speed at the edge of rotation
  • Angular Velocity: Rate of rotation in radians per second
  • Cutting Speed: Important for machining and manufacturing
How to Use the Calculator

Follow these steps to use the RPM calculator:

  • Select your calculation type (RPM from surface speed or vice versa)
  • Enter the diameter of your rotating object in inches
  • Input either the surface speed (in feet per minute) or RPM, depending on your calculation type
  • Click "Calculate" to see results for RPM, surface speed, and angular velocity
RPM Formulas

Key formulas used in RPM calculations:

  • RPM from Surface Speed:
    RPM = (Surface Speed × 12) / (π × Diameter)
  • Surface Speed from RPM:
    Surface Speed = (π × Diameter × RPM) / 12
  • Angular Velocity from RPM:
    ω (rad/s) = (RPM × 2π) / 60

Where:

  • Surface Speed is in feet per minute
  • Diameter is in inches
  • π (pi) ≈ 3.14159
  • Angular velocity (ω) is in radians per second
Frequently Asked Questions

What is surface speed and why is it important?

Surface speed is the linear speed at the edge of a rotating object. It's crucial for machining operations, as it affects tool life, surface finish, and cutting efficiency.

How do I measure RPM in practice?

RPM can be measured using a tachometer, either contact or non-contact type. Many machines also have built-in RPM displays or sensors.

Why is angular velocity important?

Angular velocity (in radians per second) is important in physics and engineering calculations, especially when dealing with rotational motion, torque, and power calculations.