Millimeters to InchesFree online conversion calculator — instant results, no sign-up
Convert millimeters to inches and back.
Sign in to save results and favorites.
About the Millimeters to Inches
The Millimeters to Inches calculator converts a length in millimeters to inches using the exact relationship of 25.4 millimeters per inch. It also shows the reverse inches-to-millimeters relationship. With the default input of 1 millimeter, the inch result is displayed as 0.03937 inches.
- Value in millimeters
- The length to convert, measured in millimeters, with a default value of 1.
Formula and method
i = m / 25.4; reverse conversion: m = i × 25.4.
- mLength in millimeters.
- iLength in inches.
Divide the millimeter value by 25.4 to obtain inches, then round for display. For the default input, 1 / 25.4 gives the displayed result of 0.03937 inches. To convert in the opposite direction, multiply the inch value by 25.4; 1 inch equals 25.4 millimeters.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Value in millimeters1 millimeters
Results
- inches0.03937
- 1 millimeters =0.03937 inches
- 1 inches =25.4 millimeters
How to use the Millimeters to Inches
- 1Enter the length in the Value in millimeters field, or leave the default value of 1.
- 2Read the inches result calculated by dividing the entered value by 25.4.
- 3Check the forward conversion row: with the default input, it reads 1 millimeters = = 0.03937 inches.
- 4Read the reverse relationship row, 1 inches = = 25.4 millimeters, to see the millimeter equivalent of one inch.
- 5For an inches-to-millimeters calculation, use the reverse formula by multiplying the inch value by 25.4.
Reading your result
The output inches = 0.03937 is the converted default input, rounded for display. The row 1 millimeters = = 0.03937 inches repeats that result with both units. The row 1 inches = = 25.4 millimeters states the reverse unit relationship; it is not the conversion of 0.03937 inches back to millimeters. The duplicated equals signs in the displayed rows should be read as a single equals sign.
Limitations
The conversion factor of 25.4 millimeters per inch is exact, but the displayed 0.03937-inch result is rounded. Converting a rounded result back may therefore not reproduce the original value exactly. Conversion does not improve the accuracy of the original measurement. Only a millimeter input is specified here; the reverse formula does not imply that a separate inch-entry field is available.
Common questions
Why does the calculator divide millimeters by 25.4?+
One inch is defined as exactly 25.4 millimeters, so dividing a millimeter length by 25.4 expresses the same length in inches.
Is 1 millimeter exactly 0.03937 inches?+
No. The exact value is 1 / 25.4 inches; 0.03937 inches is its rounded display value.
How do I convert inches back to millimeters?+
Multiply the inch value by 25.4. The reverse relationship shown here is 1 inch = 25.4 millimeters.
Does the millimeter conversion result show decimal inches or fractional inches?+
The result shown is decimal inches: the default input produces 0.03937 inches, not a ruler-style fraction.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
You might also like
Centimeters to Inches
Convert centimeters to inches and back.
Inches to Centimeters
Convert inches to centimeters and back.
Feet to Meters
Convert feet to meters and back.
Meters to Feet
Convert meters to feet and back.
Kilometers to Miles
Convert kilometers to miles and back.
Miles to Kilometers
Convert miles to kilometers and back.
Results are estimates for informational purposes and are not financial, medical or legal advice.