What is moment of inertia?

Moment of inertia (I) measures resistance to angular acceleration. For a point mass m at radius r, I = m × r². SI unit is kg·m². It appears in τ = I × α (Newton's 2nd law for rotation).

How is moment of inertia different from mass?

Mass measures resistance to linear acceleration (F = m × a). Moment of inertia measures resistance to angular acceleration and depends not just on total mass but on how mass is distributed relative to the rotation axis.

What is a slug·ft²?

Slug is the US customary unit of mass (1 slug ≈ 14.594 kg). 1 slug·ft² = 1.35582 kg·m², used in aerospace and mechanical engineering in the US customary system.

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Yes - all conversions run in JavaScript in your browser. No data is sent to any server.

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Moment of Inertia Converter

Live

From

Sig. figures:

Sci notation

Kilogram square metre

kg·m²

1(input)

Gram square centimetre

g·cm²

1.00000e+7

Gram square metre

g·m²

1000

Kilogram square centimetre

kg·cm²

10000

Tonne square metre

t·m²

0.001

Pound square foot

lb·ft²

23.7304

Pound square inch

lb·in²

3417.17

Ounce square foot

oz·ft²

379.686

Ounce square inch

oz·in²

54674.7

Slug square foot

slug·ft²

0.737561

kg·cm·s² (moment = kg·cm²)

kg·cm²

10000

g·cm·s² (moment)

g·cm·s²

1.01972e+6

Hover any row to copy or use as input.

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Convert between all common moment of inertia units in three groups: SI (kg·m², g·cm², g·m², kg·cm², t·m²), Imperial (lb·ft², lb·in², oz·ft², oz·in², slug·ft²), and Mixed/Legacy (kg·cm²). Includes moment of inertia formulas for common shapes (solid cylinder, sphere, hoop, thin rod) and real-world values for flywheels. Based on Euler's equation τ = I × α. Adjustable precision, scientific notation, swap units, copy any row.

How to Use

1Enter a moment of inertia value in the From field and choose the source unit (e.g. kg·m²)
2Select the target unit in the To dropdown (e.g. lb·ft²) to see the instant result
3Browse SI, Imperial, and Mixed/Legacy groups in the results panel
4Hover any row and click Copy or ↕ to copy or set as input
5Open the Reference panel for shape formulas (cylinder, sphere, hoop, rod) and flywheel values
6Use τ = I × α to relate inertia, torque, and angular acceleration

Features

SI group: kg·m², g·cm², g·m², kg·cm², t·m²
Imperial group: lb·ft², lb·in², oz·ft², oz·in², slug·ft²
Mixed/Legacy group: kg·cm² and g·cm·s²
Instant two-way conversion with From/To selectors and swap button
3–12 significant figures and scientific notation toggle
Reference panel with shape formulas (cylinder, sphere, hoop, rod) and Euler's equation
100% browser-based - all conversions in JavaScript

Moment of Inertia Converter

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