Millimeter to Inch Converter
Enter the value that you want to convert millimeter (mm) to inch (in) or inch to millimeter.Also written as MM to IN conversion.
1 millimeter = 0.0393701 inch
Formula: inch = millimeter value × 0.0393701
MM to IN — millimeter to inch
10 millimeter = 0.39370 inch
Popular Length Converters:
Millimeter to Inch: The Essentials
The Millimeter Explained
Millimeter (mm) is a unit of length measurement. 1 millimeter is equal to 0.0393701 inch.
The Inch Explained
Inch (in) is a unit of length measurement. 1 inch is equal to 25.4000000 millimeter.
Length Conversions in Practice
Length conversions connect the metric system used by most of the world with the imperial system still dominant in the United States, UK construction, and aviation. Architects convert between meters and feet for international projects. Machinists work in thousandths of an inch while referencing metric specifications. Runners compare kilometer race distances to miles. Screen sizes, paper formats, and fabric measurements all require frequent conversion between systems.
millimeter to inch metric conversion table
| 0.01 mm | = | 0.00039 in |
| 0.1 mm | = | 0.00394 in |
| 1 mm | = | 0.03937 in |
| 2 mm | = | 0.07874 in |
| 3 mm | = | 0.11811 in |
| 4 mm | = | 0.15748 in |
| 5 mm | = | 0.19685 in |
| 6 mm | = | 0.23622 in |
| 7 mm | = | 0.27559 in |
| 8 mm | = | 0.31496 in |
| 9 mm | = | 0.35433 in |
| 10 mm | = | 0.39370 in |
| 11 mm | = | 0.43307 in |
| 12 mm | = | 0.47244 in |
| 13 mm | = | 0.51181 in |
| 14 mm | = | 0.55118 in |
| 15 mm | = | 0.59055 in |
| 16 mm | = | 0.62992 in |
| 17 mm | = | 0.66929 in |
| 18 mm | = | 0.70866 in |
| 19 mm | = | 0.74803 in |
| 20 mm | = | 0.78740 in |
| 30 mm | = | 1.18110 in |
| 40 mm | = | 1.57480 in |
| 50 mm | = | 1.96850 in |
| 60 mm | = | 2.36220 in |
| 70 mm | = | 2.75591 in |
| 80 mm | = | 3.14961 in |
| 90 mm | = | 3.54331 in |
| 100 mm | = | 3.93701 in |
| 200 mm | = | 7.87402 in |
| 300 mm | = | 11.81102 in |
| 400 mm | = | 15.74803 in |
| 500 mm | = | 19.68504 in |
| 600 mm | = | 23.62205 in |
| 700 mm | = | 27.55906 in |
| 800 mm | = | 31.49606 in |
| 900 mm | = | 35.43307 in |
| 1000 mm | = | 39.37008 in |
How to Convert MM to IN (Millimeter to Inch)?
We can convert millimeter to inch by using an example.
Example:
Convert 20 Millimeter to Inch?
We know 1 Millimeter = 0.0393701 inch; 1 Inch = 25.4000000 millimeter.
20 millimeter = ___in
20 × 0.0393701 = 0.78740 in (we know 1 millimeter = 0.0393701 inch)
Answer:
20 millimeter = 0.78740 inch
How to Convert Millimeters to Inches (Step-by-Step)
Converting millimeters to inches is critical in manufacturing, engineering, and precision work. Since 1 inch = 25.4 mm exactly, divide millimeters by 25.4 to get inches.
- Write down the measurement in millimeters (mm).
- Divide the mm value by 25.4 (or multiply by 0.0393701).
- The result is the equivalent length in inches.
- For fractional inches, multiply the decimal by the denominator (e.g., ×16 for sixteenths).
Common Millimeter to Inch Conversions
Essential mm-to-inch conversions for machining, bolt sizes, wire gauges, and precision measurements.
| Millimeter | Inch |
|---|---|
| 1 mm | 0.03937 in |
| 3 mm | 0.118 in |
| 6 mm | 0.236 in |
| 10 mm | 0.394 in |
| 12.7 mm | 0.5 in |
| 19.05 mm | 0.75 in |
| 25.4 mm | 1 in |
| 50.8 mm | 2 in |
Solved Examples: mm to Inches
Question 1: A machining tolerance specifies 0.05 mm. What is this in inches?
Solution:
inches = mm ÷ 25.4
= 0.05 ÷ 25.4
= 0.00197 inches
≈ 0.002" (about 2 thousandths of an inch)
Answer: 0.05 mm ≈ 0.002 inches (2 thou) — a typical CNC machining tolerance
Question 2: An M8 bolt has a diameter of 8 mm. What is this in inches?
Solution:
inches = 8 ÷ 25.4
= 0.3150 inches
≈ 5/16 inch (0.3125")
Answer: 8 mm = 0.315 inches (closest standard: 5/16" = 7.94 mm)
Question 3: Rainfall measured 23 mm. Convert to inches.
Solution:
inches = 23 ÷ 25.4
= 0.906 inches
≈ just under 1 inch of rain
Answer: 23 mm ≈ 0.91 inches of rainfall (a moderately heavy rain event)
Question 4: A 14 AWG wire has a diameter of 1.628 mm. What is this in inches?
Solution:
inches = 1.628 ÷ 25.4
= 0.0641 inches
= 64.1 thou (mils)
Answer: 1.628 mm = 0.0641 inches (64.1 mils)
Practice Questions
Try solving these on your own to test your understanding:
- Convert 76.2 mm to inches. (Answer: 3 inches exactly)
- A drill bit is 4.5 mm. What is this in inches? (Answer: 0.177 inches ≈ 11/64")
- Convert 152.4 mm to inches. (Answer: 6 inches exactly)
- Rainfall of 50 mm equals how many inches? (Answer: 1.969 inches ≈ 2 inches)
- A 2.5 mm hex key — what is this in inches? (Answer: 0.0984 inches ≈ 3/32")
Machining Tolerances: mm vs Thousandths of an Inch
In precision manufacturing, tolerances are expressed in thousandths of an inch (thou/mils) in the US and in hundredths of a millimeter in metric countries. Key equivalents: 0.01 mm = 0.0004" (0.4 thou), 0.025 mm = 0.001" (1 thou), 0.05 mm = 0.002" (2 thou), 0.1 mm = 0.004" (4 thou), 0.25 mm = 0.01" (10 thou). Standard CNC tolerances of ±0.05 mm equal ±0.002" — knowing both systems prevents costly errors when reading international engineering drawings.
Metric Bolt Sizes vs Imperial Equivalents
When working with mixed fastener systems, knowing mm-to-inch equivalents prevents using the wrong wrench. Common metric bolts and closest imperial: M3 (3mm) ≈ no exact match, M4 (4mm) ≈ no exact match, M5 (5mm) ≈ close to #10, M6 (6mm) ≈ 1/4", M8 (8mm) ≈ 5/16", M10 (10mm) ≈ 3/8", M12 (12mm) ≈ 1/2", M16 (16mm) ≈ 5/8", M20 (20mm) ≈ 3/4". Note: these are approximate — never force an imperial wrench on a metric bolt.
Rainfall Measurement: mm to Inches
Weather services worldwide report rainfall in millimeters, while US forecasts use inches. Key conversions: 1 mm rain = 0.039 inches, 10 mm = 0.39 inches, 25 mm ≈ 1 inch (light-moderate rain), 50 mm ≈ 2 inches (heavy rain), 100 mm ≈ 4 inches (very heavy/flooding risk). A standard rain gauge measures to 0.2 mm precision (0.01 inch). Annual rainfall: London averages 602 mm (23.7"), New York 1268 mm (49.9"), Mumbai 2422 mm (95.4").
Key Takeaways
- Divide millimeters by 25.4 to get inches (1 inch = 25.4 mm exactly).
- Quick estimate: divide mm by 25 for approximate inches.
- 1 thou (mil) = 0.001 inch = 0.0254 mm — critical for machining.
- Metric bolts (M6, M8, M10) do NOT exactly match imperial sizes.
- 25 mm ≈ 1 inch of rainfall is a useful weather conversion.
- Wire gauges, drill bits, and sheet metal all require mm-to-inch conversion.
Millimeter to Inch Conversion Formula
inch = millimeter × 0.0393701
1 millimeter = 0.0393701 inch
1 inch = 25.4000000 millimeter
Reverse: millimeter = inch × 25.4000000
Frequently Asked Questions
How many inch are in 1 millimeter?
There are 0.0393701 inch in 1 millimeter. To convert millimeter to inch, multiply the value by 0.0393701.
How do I convert millimeter to inch?
Multiply your millimeter value by 0.0393701 to get the equivalent in inch. For example, 5 millimeter = 5 × 0.0393701 = 0.19685 inch.
How do I convert inch to millimeter?
Multiply your inch value by 25.4000000 to get the equivalent in millimeter. Alternatively, divide by 0.0393701.
What is 10 millimeter in inch?
10 millimeter is equal to 0.39370 inch.
What is 100 millimeter in inch?
100 millimeter is equal to 3.93701 inch.