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Calcimator

Flywheel Energy Calculator

Calculate kinetic energy stored in a flywheel. Determine moment of inertia, angular velocity, and energy in ft·lb, Joules, and Wh.

Inputs

lb
in
in
RPM

Results

Kinetic Energy

39,409.67 ft·lb

Energy

14.84 Wh

Moment of Inertia3,700 lb·in²
Kinetic Energy53,432.35 J
Angular Velocity314.16 rad/s
How to Use This Calculator
  1. Enter the Flywheel Mass in lb — heavier flywheels store proportionally more energy.
  2. Enter the Outer Radius in inches. Energy scales with radius squared, so a larger outer radius dramatically increases storage.
  3. Enter the Inner Radius (Bore) in inches — set to 0 for a solid disk flywheel.
  4. Enter the Rotational Speed in RPM. Energy scales with RPM squared, so doubling speed quadruples stored energy.
  5. Review Kinetic Energy in ft·lb and Joules, and stored Energy in Wh for direct comparison with battery systems.
  6. Use the Moment of Inertia (lb·in²) value for dynamic and shaft-load calculations.

How the result changes with Rotational Speed

Rotational SpeedKinetic EnergyEnergy
10,001437,972.83 ft·lb164.95 Wh
35,0015,364,400.85 ft·lb2,020.32 Wh
65,00018,500,651.85 ft·lb6,967.65 Wh
90,00035,468,705.32 ft·lb13,358.09 Wh

What each input means

Flywheel Mass
Total mass of the flywheel. Heavier flywheels store more energy at the same speed.
Outer Radius
Outside radius of the flywheel. Energy storage scales with radius squared.
Inner Radius (Bore)
Inner bore radius. Set to 0 for a solid disk flywheel.
Rotational Speed
Operating speed of the flywheel. Energy scales with RPM squared — doubling speed quadruples energy.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Flywheel Mass = 50, Outer Radius = 12, Inner Radius (Bore) = 2, Rotational Speed = 3000 = 4 input(s) provided
  2. Calculate Kinetic Energy
    39409.67 = 39409.67
  3. Calculate Energy
    Energy
    14.842 = 14.842
  4. Calculate Moment of Inertia
    3700 = 3700
  5. Calculate Kinetic Energy
    Kinetic Energy
    53432.35 = 53432.35

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