Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Unit Converters
Millimeters to Inches Converter (mm to in)
Millimeters
Going the other way? Open the reverse converter
mm → in
1 in
Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
- You typed
- 25.4 mm
- One in is
- 25.4 mm
- How it’s calculated
- inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
Millimeters to Inches conversion table
Common mm values in in. Same factor as the converter above: inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
| Millimeters | Inches |
|---|---|
| 0.25 mm | 0.00984 in |
| 0.5 mm | 0.01969 in |
| 1 mm | 0.03937 in |
| 2 mm | 0.07874 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.3937 in |
| 20 mm | 0.7874 in |
| 25 mm | 0.98425 in |
| 25.4 mm | 1 in |
| 30 mm | 1.1811 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.93701 in |
Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Millimeters
The “Millimeters” value used in this tool’s formula. Adjust it to see results update live.
inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
Wrench sizes, phone specs, and rain totals often arrive in mm. Hardware aisles in the US still think in fractions of an inch. Divide mm by 25.4. A “25 mm” socket is not 1 inch; it is 0.984 in.
How this calculator works
Wrench sizes, phone specs, and rain totals often arrive in mm. Hardware aisles in the US still think in fractions of an inch. Divide mm by 25.4. A “25 mm” socket is not 1 inch; it is 0.984 in. inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch. Scenario: Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
Scenario: Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
When to use this Millimeters to Inches
Common use cases
- Wrench sizes, phone specs, and rain totals often arrive in mm. Hardware aisles in the US still think in fractions of an inch. Divide mm by 25.4. A “25 mm” socket is not 1 inch; it is 0.984 in.
- Sanity-check with this scenario: Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
- The relationship is: inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
Localized examples
- Unit Converters: the example on this page uses the same formula as the widget.
What you get
- Fields: Millimeters
- inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
- Scenario on the page: Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
How to Convert Millimeters to Inches
- 1Enter Millimeters. Use the values you have, not a catalog average, unless that is all you know.
- 2inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
- 3Scenario: Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
- 4Check which dictionary the other person is using — US or UK, decimal or 1,024 — then trust the number.
Governing formula
inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.
Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
Rain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
Variable definitions
- value
Millimeters
The “Millimeters” field. Default 25.4; typical range 0–100000.
- The conversion (inches = millimeters ÷ 25.4. 25.4 mm is exactly one inch.) does not pick US vs UK gallons, SI vs binary megabytes, or Mach at altitude for you. Read the footnote on the page.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Convert to decimal inches, then pick the nearest 16th or 32nd. This page stays decimal so you can see the error.
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- Inches to MillimetersThe international inch is exactly 25.4 mm. That 1959 agreement is why a 1/4 in bolt is 6.35 mm, not “about 6.” Use this when a US drawing meets a metric mill. Fractions of an inch still need you to divide the fraction first.
- BMI Metric and ImperialBMI = kg / m² = 703 × lb / in². Same index, two unit systems. It does not know muscle, bone, or why a powerlifter and a couch get the same number. Categories are public-health bins, not a diagnosis.
- Bra Size ConverterBand in inches (US/UK) and cup letter. EU bands are centimeters rounded to 5 (34 → 75). Cup letters drift after D: UK DD vs US DD/E is a forum war. Sister sizes (34C / 32D) share cup volume, not this converter’s job.
- Centimeters to InchesHeight charts, inseam tables, and sewing patterns swap cm and inches constantly. Divide cm by 2.54. A 180 cm person is about 5 ft 11 in — the leftover 0.16 in is why both sides of a doorway argue about the last fraction.
- Centimeters to Pixelspx = (cm / 2.54) × DPI. A 10 cm bar at 300 DPI is 1,181 px. A4 width 21 cm at 300 DPI is 2,480 px. Packaging die-lines still want millimeters and bleed; this is the raster step.
- Cubic Inches to Cubic CentimetersEngine displacement: a “350” small-block is 350 in³, about 5.7 L (5,735 cc). Multiply in³ by 16.387. One liter is 1,000 cm³. This is why 5.0 L and 302 in³ show up on the same valve cover.
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4.8
out of 5.0
4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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