Convert mm to inches
The mm to inches converter shows the exact imperial length using the fixed relation 1 inch = 25.4 millimeters. It’s handy when metric specs meet U.S. hardware—think woodworking cut lists, 3D-printing parts sourced abroad, tool clearances, or comparing product dimensions across regions.
Enter a value in millimeters and get an immediate inch reading tailored for real-world use (decimal and shop-friendly fractions). The goal is fast, error-free translation so you keep measurements consistent, order the right components, and avoid costly miscuts. Type a size to convert and move on with confidence.
Convert millimeters (mm) to inches — with decimals, feet-inches format, and fraction rounding.
Your conversion
Converted mm to inches values
How our mm to inches converter works
Formulas, steps & assumptions
Formula: inches = millimeters ÷ 25.4 (exact).
Rounding: we round decimal inches to your chosen decimal places. Fractional inches are rounded to the nearest 1/N.
Limitations: for tight tolerances, keep values in mm during design and only convert for fabrication notes.
Results interpretation: who benefits
- DIY & construction: convert metric plans to tape-measure inches with common fractions.
- Manufacturing: keep mm in CAD; publish decimal inches for shop notes where required.
- 3D printing: verify STL dimensions in inches before ordering hardware listed in imperial sizes.
Use cases & examples
Example 1 — 12 mm bolt: 12 ÷ 25.4 ≈ 0.4724 in → nearest 1/16″ ≈ 15/32″.
Example 2 — 200 mm shelf depth: 200 ÷ 25.4 ≈ 7.8740 in → 7 in + 0.8740 in → 7⅞″ (nearest 1/8″).
Example 3 — 762 mm door: 762 ÷ 25.4 = 30.0000 in exactly (30″).
mm to inches — FAQ
How do you convert mm to inches?
Divide millimeters by 25.4 (exact). We show decimal inches, feet-inches, and the nearest fractional inch.
What fraction should I use (1/16 vs 1/32 vs 1/64)?
Use 1/16″ for general carpentry, 1/32″ for finer trim, and 1/64″ when you need very close approximations.
Why do my decimal inches differ from the fraction?
Fractions are rounded to the nearest 1/N, while decimal inches are rounded to your chosen places. They may differ slightly by design.
Can I convert negative values?
Yes. We preserve the sign in all outputs.
Is 25.4 mm exactly 1 inch?
Yes—by definition. That’s why conversions are reliable across industries.
Do you support inches to mm?
This page focuses on mm → inches. You can reverse the formula: inches × 25.4 = mm.
How to convert millimeters to inches
- Enter a value in millimeters.
- Choose your decimal places for inches.
- Optionally turn on nearest fractional inch and pick a denominator.
- Read decimal inches, feet-inches, and fractional inches in the result card and banner.
- Use Copy link with inputs to save/share your setup.
Millimeters to Inches: practical rules, tolerances, and fractional rounding
We built our mm-to-inch converter to speed up real-world work. Plans, cut lists, and vendor specs don’t always use the same system, so fast, transparent conversion prevents mistakes on the bench and in the field.
The exact relationship
One inch equals 25.4 mm exactly. That definition anchors every conversion we show. Because it’s exact, any rounding you see is your preference—never a hidden assumption.
When to keep decimals vs fractions
Fractions match tape measures and common shop talk. Decimals are best for machining and printing where instruments read in 0.001″ or better. We let you choose both and keep them consistent.
Tolerance and fit
For tight fits, avoid switching systems mid-design. Keep a master in mm, then publish converted values with tolerances (e.g., ±0.25 mm / ±0.010″).
Reducing errors
Most mistakes come from mixing whole inches with fractional remainders. Showing feet-inches, decimals, and a nearest fraction side-by-side makes mismatches obvious before you cut.