Convert Millimeters to Inches
Instant, exact conversion from millimeters (mm) to decimal and fractional inches ("). Engineered for machinists, 3D printing enthusiasts, woodworkers, and architects.
¿Qué es «Milímetros a pulgadas»?
«Milímetros a pulgadas» es la conversión entre dos unidades de longitud: el milímetro (mm), unidad base del sistema métrico decimal, y la pulgada (in), propia del sistema imperial. Un milímetro equivale exactamente a 0,0393701 pulgadas, o dicho de forma directa, una pulgada son exactamente 25,4 mm. Esta equivalencia es esencial en ingeniería, arquitectura, carpintería y fabricación digital.
Millimeter to Inch Equivalencies
MM to inch equivalencies show the direct relationship between metric and imperial systems for dimensional measurements across workshops, design, and manufacturing.
📏 Dynamic Dual-Scale Ruler (mm / in)
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One millimeter (mm) equals 0.001 m, while one inch (in / ") corresponds to 25.4 mm (2.54 cm). Measuring instruments such as calipers, tape measures, and micrometers combine both scales to guarantee exact tolerances in workshop and production.
How MM to Inches Conversion Works
Converting millimeters to inches takes 3 simple steps: identify the measurement, apply the exact formula, and express the final result.
Identify the value
Take the millimeter measurement from your caliper, technical blueprint, or workshop rule.
Divide by 25.4
Apply the international exact conversion factor established by the SI standard.
Get the result
Express the value in decimal inches or round to the nearest imperial workshop fraction.
The official SI formula is exact: Inches = mm ÷ 25.4. The resulting decimal easily converts into standard workshop fractions (1/2", 1/4", 1/8", 1/16", 1/32", 1/64") for carpentry, turning, and CNC machining.
Millimeters to Inches Conversion Table
Lookup standard metric dimensions with corresponding decimal and fractional inch equivalents.
| Millimeters (mm) | Inches (Decimal) | Inches (Fraction) |
|---|---|---|
| 1 mm | 0.0394" | ≈ 3/64" |
| 2 mm | 0.0787" | ≈ 5/64" |
| 3 mm | 0.1181" | ≈ 1/8" |
| 4 mm | 0.1575" | ≈ 5/32" |
| 5 mm | 0.1969" | ≈ 13/64" |
| 6 mm | 0.2362" | ≈ 15/64" |
| 6.35 mm | 0.2500" | = 1/4" |
| 8 mm | 0.3150" | ≈ 5/16" |
| 9.525 mm | 0.3750" | = 3/8" |
| 10 mm | 0.3937" | ≈ 25/64" |
| 12 mm | 0.4724" | ≈ 15/32" |
| 12.7 mm | 0.5000" | = 1/2" |
| 15 mm | 0.5906" | ≈ 19/32" |
| 16 mm | 0.6299" | ≈ 5/8" |
| 19.05 mm | 0.7500" | = 3/4" |
| 20 mm | 0.7874" | ≈ 25/32" |
| 22 mm | 0.8661" | ≈ 7/8" |
| 25 mm | 0.9843" | ≈ 63/64" |
| 25.4 mm | 1.0000" | = 1" |
| 30 mm | 1.1811" | ≈ 1 3/16" |
| 35 mm | 1.3780" | ≈ 1 3/8" |
| 38.1 mm | 1.5000" | = 1 1/2" |
| 40 mm | 1.5748" | ≈ 1 37/64" |
| 45 mm | 1.7717" | ≈ 1 25/32" |
| 50 mm | 1.9685" | ≈ 1 31/32" |
| 50.8 mm | 2.0000" | = 2" |
| 60 mm | 2.3622" | ≈ 2 23/64" |
| 70 mm | 2.7559" | ≈ 2 3/4" |
| 75 mm | 2.9528" | ≈ 2 61/64" |
| 76.2 mm | 3.0000" | = 3" |
| 80 mm | 3.1496" | ≈ 3 5/32" |
| 90 mm | 3.5433" | ≈ 3 35/64" |
| 100 mm | 3.9370" | ≈ 3 15/16" |
| 150 mm | 5.9055" | ≈ 5 29/32" |
| 200 mm | 7.8740" | ≈ 7 7/8" |
| 254 mm | 10.0000" | = 10" |
| 304.8 mm | 12.0000" | = 12" |
| 500 mm | 19.6850" | ≈ 19 11/16" |
| 1000 mm | 39.3701" | ≈ 39 3/8" |
Practical Length Conversion Examples
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Common Questions on mm to inches
Everything you need to know about millimeter and inch conversions, fractions, and manufacturing standards.
How many inches are in a millimeter?
One millimeter equals exactly 0.03937 inches (1 ÷ 25.4), which corresponds approximately to 1/25 of an inch in fractional imperial notation.
What is the exact factor to convert mm to inches?
The exact factor is 25.4 (Inches = mm ÷ 25.4). It is an exact, unrounded constant defined by the 1959 international agreement and endorsed by NIST.
How do you convert millimeters with decimals to inches?
Apply the same formula by dividing by 25.4. For example: 0.5 mm ÷ 25.4 = 0.0197" and 12.7 mm ÷ 25.4 = 0.5" (exactly 1/2").
How much is 25 mm in inches?
25 mm equals 0.9843 inches (≈ 63/64"). Although in everyday measurements it is approximated to 1", the 0.4 mm difference is critical in manufacturing and calibration.
How much is 100 mm expressed in inches?
100 mm equals 3.9370 inches (≈ 3 15/16"), as well as 10 cm or 0.1 m. It is a standard dimension in screen sizes, lumber, and mechanical components.
Why do inches often appear in decimal format?
Because dividing by 25.4 produces direct decimal values (0.3937"). Engineering prefers decimals for precision, while woodworking and plumbing use fractions (1/8", 1/4", 1/2").
Can very small measurements be converted from mm to inches?
Yes, using the exact same formula (mm ÷ 25.4). For example: 0.05 mm = 0.00197", 0.1 mm = 0.00394", and 0.2 mm = 0.00787", typical in microelectronics and micrometers.
What is the difference between a decimal inch and a fractional inch?
Both represent the exact same length: decimal format uses point notation (0.5") for CAD and technical drawings, while fractional notation uses fractions (1/2") for hand tools and tape measures.
Where are millimeter measurements typically used?
In mechanical engineering, medicine, 3D printing, manufacturing, and technical drafting in more than 190 countries adhering to the International System of Units (SI).
What industries use both millimeters and inches?
7 key industries: manufacturing, automotive, aerospace, electronics, carpentry, plumbing, and 3D printing, where metric threads frequently coexist with imperial pipes and drill bits.