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Gurukrupa Enterprises
Unit Converters

Inch to mm Converter

Convert inches to millimetres using the exact 25.4 mm/inch relationship.

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About this calculator

This calculator converts length from inches to millimetres using the exact conversion of 1 inch = 25.4 mm — useful for machining metric parts from imperial drawings or specifying imported imperial fasteners in metric terms.

Formula

mm = inch × 25.4
  • inchLength — inches
  • mmLength — millimetres

Worked Example

Given: A bolt is 1 inch long.

Result: 1 × 25.4 = 25.4 mm.

How to Use

  1. Enter the length in inches (decimal, e.g. 0.5 for 1/2 inch).
  2. Click Calculate to see the equivalent length in millimetres.

Important Assumptions

  • Exact conversion, no rounding error.

Common Mistakes

  • Entering a fraction like 1/2 directly instead of its decimal equivalent (0.5).

Frequently Asked Questions

How do I convert a fraction like 3/4 inch?

Convert the fraction to decimal first (3÷4 = 0.75) and enter 0.75 as the input.

These calculators are provided for informational and estimation purposes. Results depend on the assumptions and input values used. Always verify critical engineering calculations against applicable standards, manufacturer specifications, site measurements, and qualified professional advice.