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Calculate flywheel torque from inertia, acceleration, mass, radius, RPM, or power with our easy Flywheel Torque Calculator.
| Formula | Use When You Know | Notes |
|---|---|---|
| T = I × α | Moment of inertia I, angular acceleration α | Fundamental flywheel torque equation |
| α = 2π(N₂−N₁) ÷ 60t | Speed change N₁→N₂ over time t | Converts rpm change to α |
| I = k·m·r² | Mass m, radius r, shape factor k | k depends on flywheel geometry (0.5 solid disk, 1.0 thin ring, etc.) |
| T = P ÷ ω = 30P ÷ πN | Power P, speed N | Alternative when power/speed are known instead of inertia |
| E = ½Iω² | — | Rotational energy — a separate quantity from torque |
The Flywheel Torque Calculator helps you find torque from flywheel inertia, angular acceleration, mass, radius, speed change, or power. It uses three core methods.
You can enter moment of inertia and angular acceleration. You can also enter flywheel mass, radius, shape factor, and speed change. A third option finds torque from power and RPM.
The calculator converts your units first. It then gives the final torque in N·m or another selected torque unit. This makes flywheel torque calculations fast and easy.
The main flywheel torque formula is:
T = I × α
Here, T is torque in N·m. I is moment of inertia in kg·m². α is angular acceleration in rad/s².
If you know the initial and final speed, first find angular acceleration:
α = (ω₂ − ω₁) / t
Angular speed is:
ω = 2πN / 60
So the combined formula becomes:
T = I × [2π(N₂ − N₁) / (60t)]
For a flywheel with known mass, radius, and shape factor, the calculator uses:
I = k × m × r²
The torque formula then becomes:
T = k × m × r² × [2π(N₂ − N₁) / (60t)]
The shape factor k depends on the flywheel design. A solid disk uses k = 0.5. A thin ring uses k = 1.0. A solid sphere uses k = 0.4. The calculator also provides k = 0.7 for a thick-rimmed wheel.
For power and speed, the calculator uses:
T = P / ω
Using power in watts and speed in RPM:
T = 30P / (πN)
This is useful as a power and torque calculator for rotating systems.
Choose the calculation mode that matches your known values. You can use inertia and acceleration, mass and radius, or power and speed.
Enter the required values. For the inertia method, enter I and either angular acceleration or the starting speed, ending speed, and time.
For the mass and radius method, enter the flywheel mass, effective radius, shape factor, initial RPM, final RPM, and time.
For the power method, enter the power and rotational speed. The calculator supports watts, kilowatts, and horsepower.
Select your output torque unit and calculate. The calculator converts the result from its internal N·m value to your chosen unit.
Suppose a flywheel has a moment of inertia of 0.625 kg·m². Its speed rises from 600 RPM to 1,200 RPM in 5 seconds.
First, find the initial angular speed:
ω₁ = 2π × 600 / 60
ω₁ = 62.83 rad/s
Next, find the final angular speed:
ω₂ = 2π × 1,200 / 60
ω₂ = 125.66 rad/s
Now calculate angular acceleration:
α = (125.66 − 62.83) / 5
α = 12.57 rad/s²
Finally:
T = I × α
T = 0.625 × 12.57
T ≈ 7.85 N·m
So, the flywheel torque is about 7.85 N·m.
This calculator focuses on rotational and inertial torque. It does not calculate flywheel bolt torque specs, torque converter-to-flywheel bolt settings, engine-to-wheel torque, or vehicle-specific flywheel torque specifications.
The Flywheel Torque Calculator gives a simple way to calculate rotational torque. Its three main methods are T = I × α, T = k × m × r² × [2π(N₂ − N₁) / (60t)], and T = 30P / (πN).
Use the first method when inertia and acceleration are known. Use the second when you know flywheel mass, radius, shape, and speed change. Use the power method when power and RPM are available.
For vehicle work, terms such as engine torque to wheel torque, flywheel horsepower, torque converter calculations, and flywheel bolt torque specs describe different calculations. They should not be confused with the inertial flywheel torque calculated here.
The basic formula is T = I × α. Torque equals moment of inertia multiplied by angular acceleration.
First convert RPM to angular speed using ω = 2πN / 60. Then calculate α = (ω₂ − ω₁) / t. Finally use T = I × α.
Calculate inertia with I = k × m × r². Then multiply inertia by angular acceleration to get torque.
Yes. Convert horsepower to watts, then use T = 30P / (πN), where P is watts and N is RPM.
No. Flywheel torque from this calculator describes rotational torque. Flywheel bolt torque specs are fastener tightening values and depend on the engine, flywheel, bolt type, and manufacturer specifications.
No. Engine torque to wheel torque requires drivetrain information such as gear ratio, final drive ratio, and transmission efficiency. This calculator focuses on flywheel rotational torque.