Physics

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Mass Moment of Inertia Calculator.

Calculate standard rigid-body moments about the stated axis/model.

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Set your values

Results update as you type.

02 / ANSWER

Body model

Mass

Radius / distance

Rod / cylinder length

inertia

0.00000000

Results update automatically as you type.

Calculate standard rigid-body moments about the stated axis/model.

Use Cases

Engineering design and analysis

Quickly compute the moment of inertia for common mechanical components like shafts, disks, or rods to predict rotational behavior.

Example: A solid steel disk of 5 kg and radius 0.2 m has I = 0.1 kg·m².

Physics homework and study

Verify textbook problems or check your manual calculations for standard shapes.

Example: Check the moment of inertia of a thin rod about its end with mass 2 kg and length 1 m.

Frequently Asked Questions

What is mass moment of inertia?: Mass moment of inertia measures an object's resistance to rotational acceleration about an axis. It depends on the mass and its distribution relative to the axis. This calculator computes it for standard shapes using the selected body model.
How do I use this calculator?: Select a body model (e.g., solid disk about center), enter the mass in kg, and provide the required dimensions: radius/distance in meters for point mass, disk, or cylinder, and length in meters for rod or cylinder. The calculator then applies the standard formula for that shape.
What units does the calculator use?: Mass must be entered in kilograms (kg), and all dimensions (radius/distance and length) in meters (m). The result is given in kg·m², the SI unit for moment of inertia.

Tips & Common Mistakes

Tips

Ensure mass is in kilograms and dimensions in meters to get results in kg·m².
For a thin rod, choose the correct axis: about center or about end, as formulas differ.
For a solid cylinder about its axis, only the radius matters; length is not used.
For a point mass, the 'radius/distance' is the perpendicular distance from the axis.

Common Mistakes to Avoid

Using the wrong formula for the selected body model, e.g., using rod about center for rod about end.
Entering length for a disk or point mass, which is not required and may cause confusion.
Forgetting to convert units (e.g., using cm instead of meters) leading to incorrect results.

Last updated: August 13, 2026

Use Cases

Engineering design and analysis

Quickly compute the moment of inertia for common mechanical components like shafts, disks, or rods to predict rotational behavior.

Example: A solid steel disk of 5 kg and radius 0.2 m has I = 0.1 kg·m².

Physics homework and study

Verify textbook problems or check your manual calculations for standard shapes.

Example: Check the moment of inertia of a thin rod about its end with mass 2 kg and length 1 m.

Frequently Asked Questions

What is mass moment of inertia?

Mass moment of inertia measures an object's resistance to rotational acceleration about an axis. It depends on the mass and its distribution relative to the axis. This calculator computes it for standard shapes using the selected body model.

How do I use this calculator?

Select a body model (e.g., solid disk about center), enter the mass in kg, and provide the required dimensions: radius/distance in meters for point mass, disk, or cylinder, and length in meters for rod or cylinder. The calculator then applies the standard formula for that shape.

What units does the calculator use?

Mass must be entered in kilograms (kg), and all dimensions (radius/distance and length) in meters (m). The result is given in kg·m², the SI unit for moment of inertia.

Tips & Common Mistakes

Tips

Ensure mass is in kilograms and dimensions in meters to get results in kg·m².
For a thin rod, choose the correct axis: about center or about end, as formulas differ.
For a solid cylinder about its axis, only the radius matters; length is not used.
For a point mass, the 'radius/distance' is the perpendicular distance from the axis.

Common Mistakes to Avoid

Using the wrong formula for the selected body model, e.g., using rod about center for rod about end.
Entering length for a disk or point mass, which is not required and may cause confusion.
Forgetting to convert units (e.g., using cm instead of meters) leading to incorrect results.

Use Cases

Engineering design and analysis

Quickly compute the moment of inertia for common mechanical components like shafts, disks, or rods to predict rotational behavior.

Example: A solid steel disk of 5 kg and radius 0.2 m has I = 0.1 kg·m².

Physics homework and study

Verify textbook problems or check your manual calculations for standard shapes.

Example: Check the moment of inertia of a thin rod about its end with mass 2 kg and length 1 m.

Frequently Asked Questions

What is mass moment of inertia?

How do I use this calculator?

What units does the calculator use?

Mass must be entered in kilograms (kg), and all dimensions (radius/distance and length) in meters (m). The result is given in kg·m², the SI unit for moment of inertia.

Tips & Common Mistakes

Tips

Ensure mass is in kilograms and dimensions in meters to get results in kg·m².
For a thin rod, choose the correct axis: about center or about end, as formulas differ.
For a solid cylinder about its axis, only the radius matters; length is not used.
For a point mass, the 'radius/distance' is the perpendicular distance from the axis.

Common Mistakes to Avoid

Using the wrong formula for the selected body model, e.g., using rod about center for rod about end.
Entering length for a disk or point mass, which is not required and may cause confusion.
Forgetting to convert units (e.g., using cm instead of meters) leading to incorrect results.