Rotational Energy Calculator

Find kinetic energy for rotating parts in seconds. Select a model and enter your data. Get clear steps, units, and shareable downloads instantly today.

Calculator
Pick the data you already know.
Controls rounding in the results table.
Units used here: J, kJ, Wh. Inertia is kg·m². Use rad/s or rpm for angular speed.
Use shape mode when I is unknown.
Unit: kg·m²
All dimensions are in meters.
Unit: kg
Used by disks, hoops, spheres.
Used by rods.
Unit: N·m
Unit: kg·m²/s
Unit: kg·m²
Example data
Scenario I (kg·m²) ω (rad/s) Energy (J)
Small flywheel 0.18 125.66 1420.0
Robot wheel assembly 0.012 62.83 23.7
Machinery drum 1.40 41.89 1227.0
Tip: Convert rpm to rad/s using ω = 2π·rpm/60.
Formula used
  • E = ½ I ω² where E is rotational energy (J).
  • ω = 2π·rpm/60 to convert rpm to rad/s.
  • E = τ θ for rotational work when torque is constant.
  • E = L²/(2I) when angular momentum is known.
Common inertia models: disk/cylinder I=½mr², hoop I=mr², solid sphere I=2/5mr², shell I=2/3mr², rod center I=1/12mL², rod end I=1/3mL².
How to use this calculator
  1. Select a method that matches your available measurements.
  2. Enter values with the correct units, then choose rounding.
  3. For inertia mode, either enter I or select a shape.
  4. Press Calculate to see results above the form.
  5. Use the download buttons to save CSV or PDF reports.
Note: Results assume rigid-body rotation and consistent units.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.