How do I convert millimetres to inches?

Divide millimetres by 25.4 to get inches. 10 mm ÷ 25.4 ≈ 0.3937 in.

How do I convert inches back to millimetres?

Use the swap button, or apply the reverse factor: in × 25.4 = mm.

Yes. 1 inch is exactly 25.4 mm.

Convert millimetres to inches instantly — useful for tools, screws and screen sizes.

In short

Divide millimetres by 25.4 to get inches. For example, 10 mm ÷ 25.4 ≈ 0.3937 in.

How do I convert millimetres to inches?: Divide millimetres by 25.4 to get inches. 10 mm ÷ 25.4 ≈ 0.3937 in.
How do I convert inches back to millimetres?: Use the swap button, or apply the reverse factor: in × 25.4 = mm.
Is the conversion exact?: Yes. 1 inch is exactly 25.4 mm.