LengthInches to Millimeters

Inches to Millimeters

Methodology·How We Verify

Snapshot

1 Inch equals 25.4 Millimeters.

Reference basis: This conversion uses exact modern length definitions anchored to meters.
Example: For 0.1 Inches, the result equals 2.54 Millimeters.

Interactive conversion

Converter Calculator

Decimals: 1.5 or 1,5. Fractions: 1/2. Scientific notation: 1e3. Write 1000 without grouping separators.

25.4 Millimeters

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API and AI agent access

Inches to Millimeters.

Machine-readable identifiers

Conversion family: length
Source unit: inch
Target unit: millimeter

Use these identifiers in the API request. Sources and model limits also apply to software clients.

Example API request and response

POST /api/v1/convert

Request

{
  "family": "length",
  "value": 1,
  "from": "inch",
  "to": "millimeter"
}

Essential response

{
  "ok": true,
  "conversion": {
    "family": "length",
    "value": 1,
    "from": "inch",
    "to": "millimeter",
    "result": {
      "raw": 25.4,
      "display": "25.4"
    },
    "canonicalPath": "/length/inches-to-millimeters/"
  }
}

API, OpenAPI and WebMCP documentation

Explanation

Multiply inches by 25.4 because the international inch equals exactly 25.4 millimeters.

Method & Reference

Method basis: exact conversion formula shown in Snapshot.
Applied factor: 1 Inch = 25.4 Millimeters (using exact modern length definitions anchored to meters).
Consistency rule: calculator output and table values use the same constants and rounding policy.

Common Conversion Values

Inches	Millimeters
0.1	2.54
1/4	6.35
1/2	12.7
1	25.4
2	50.8
5	127
10	254
25	635
50	1,270
100	2,540

Questions & answers

Frequently Asked Questions

What is 1 inch in millimeters?

1 Inch equals 25.4 Millimeters on this page.

Is there a reverse Millimeters to Inches page?

Yes. Use the mirror Millimeters to Inches page to convert in the opposite direction with the same fixed length definitions.