About this converter
Moment of inertia measures how strongly a body resists angular acceleration about an axis. The SI unit is kilogram square meter (kg·m²), and 1 kg·cm² equals 0.0001 kg·m² because 1 cm² equals 0.0001 m².
This converter supports metric mass-length-squared units, imperial mass-length-squared units, and force-based engineering inertia units. Mechanical engineers, CAD designers, machine builders, robotics teams, and physics students use these conversions for flywheels, shafts, wheels, pulleys, and rotating assemblies.
How to Use This Converter
- Enter the moment of inertia value.
- Select the source unit from the From menu.
- Select the target unit from the To menu.
- Read the converted result and formula line.
- Use Swap to reverse the selected units.
Units Covered
| Unit | Symbol | Common Use |
|---|---|---|
| Kilogram square meter | kg·m² | SI rotational dynamics, CAD output, and machine design. |
| Kilogram square centimeter | kg·cm² | Smaller metric components and legacy mechanical tables. |
| Kilogram square millimeter | kg·mm² | Precision parts, shafts, and compact rotating components. |
| Gram square centimeter | g·cm² | Small mechanisms, lab examples, and educational calculations. |
| Gram square millimeter | g·mm² | Very small parts and micro-mechanical inertia estimates. |
| Kilogram-force meter square second | kgf·m·s² | Metric-force dynamics references and older engineering texts. |
| Kilogram-force centimeter square second | kgf·cm·s² | Metric-force inertia for smaller rotating parts. |
| Ounce square inch | oz·in² | Small imperial rotating components and product specs. |
| Ounce-force inch square second | ozf·in·s² | Force-based imperial dynamics references. |
| Pound square foot | lb·ft² | Imperial machinery, wheels, and larger rotating assemblies. |
| Pound-force foot square second | lbf·ft·s² | US force-based rotational dynamics calculations. |
| Pound square inch | lb·in² | Imperial component drawings and compact machine parts. |
| Pound-force inch square second | lbf·in·s² | Imperial force-based inertia for small mechanisms. |
| Slug square foot | slug·ft² | US engineering dynamics with slug mass units. |
How to Convert kg·m² to lb·ft²
Kilogram square meters to pound square feet
For example, 2 kg·m² / 0.04214011 = 47.4602 lb·ft².
Pound square feet to kilogram square meters
For example, 100 lb·ft² x 0.04214011 = 4.21401 kg·m².
When You Need to Convert Moment of Inertia
CAD software may output inertia in kg·m² while a machine design reference uses lb·ft². A rotor listed as 0.75 kg·m² equals 17.7976 lb·ft², letting engineers compare vendor data without changing the model.
Motor and gearbox sizing often uses the relationship torque = inertia x angular acceleration. If a flywheel inertia is converted to SI units first, a designer can pair it with rad/s² acceleration and calculate required torque in N·m.
Small mechanisms such as pulleys, gears, and test fixtures may use g·cm² or oz·in² because kg·m² values become tiny. A value of 250,000 g·cm² equals 0.025 kg·m², which is easier to use in SI equations.