Convert Millimeters to Inches, Feet & More
Divide by 25.4. That’s the whole conversion — one inch is 25.4 mm exactly, so any millimeter value ÷ 25.4 gives you inches. Enter a number below and you get the decimal and the nearest fraction together, no second click.
Length Converter
Convert millimeters & more
Common conversions
Real-time conversion across millimeters, centimeters, meters, kilometers, inches, feet, yards and miles. Results round to 4 significant figures; feet & inches show the height-style breakdown.
How to convert mm to inches?
The rule is one division:
inches = mm ÷ 25.4
Go the other way and you multiply instead: mm = inches × 25.4. One millimeter works out to 0.03937 in, which is why a metric number always looks a little smaller once it crosses over.
Worked example: 50 mm ÷ 25.4 = 1.9685 in.
The 25.4 isn’t a rounded-off average — it’s the definition set in 1959, so the decimal is as accurate as you care to take it. The fraction is the part that gets rounded. A tape measure only carries so many ticks, so the tool snaps the result to the nearest 1/16, 1/32, or 1/64, whichever you pick. Use the decimal for the math; use the fraction at the bench, the tape measure, or the wrench.
mm to inches conversion chart
The values people actually look up, decimal and fraction side by side. Fine steps through the first 10 mm, then the common sizes from there up. Fractions below are to the nearest 1/32; for anything not listed, run it through the field above — same math.
| mm | Inches (decimal) | Nearest fraction |
|---|---|---|
| 0.5 mm | 0.0197″ | 1/32″ |
| 1 mm | 0.0394″ | 1/32″ |
| 1.5 mm | 0.0591″ | 1/16″ |
| 2 mm | 0.0787″ | 3/32″ |
| 2.5 mm | 0.0984″ | 3/32″ |
| 3 mm | 0.1181″ | 1/8″ |
| 3.5 mm | 0.1378″ | 1/8″ |
| 4 mm | 0.1575″ | 5/32″ |
| 4.5 mm | 0.1772″ | 3/16″ |
| 5 mm | 0.1969″ | 3/16″ |
| 5.5 mm | 0.2165″ | 7/32″ |
| 6 mm | 0.2362″ | 1/4″ |
| 6.5 mm | 0.2559″ | 1/4″ |
| 7 mm | 0.2756″ | 9/32″ |
| 7.5 mm | 0.2953″ | 9/32″ |
| 8 mm | 0.3150″ | 5/16″ |
| 8.5 mm | 0.3346″ | 11/32″ |
| 9 mm | 0.3543″ | 11/32″ |
| 9.5 mm | 0.3740″ | 3/8″ |
| 10 mm | 0.3937″ | 13/32″ |
| 11 mm | 0.4331″ | 7/16″ |
| 12 mm | 0.4724″ | 15/32″ |
| 13 mm | 0.5118″ | 1/2″ |
| 14 mm | 0.5512″ | 9/16″ |
| 15 mm | 0.5906″ | 19/32″ |
| 16 mm | 0.6299″ | 5/8″ |
| 17 mm | 0.6693″ | 21/32″ |
| 18 mm | 0.7087″ | 23/32″ |
| 19 mm | 0.7480″ | 3/4″ |
| 20 mm | 0.7874″ | 25/32″ |
| 22 mm | 0.8661″ | 7/8″ |
| 24 mm | 0.9449″ | 15/16″ |
| 25 mm | 0.9843″ | 31/32″ |
| 30 mm | 1.1811″ | 1 3/16″ |
| 32 mm | 1.2598″ | 1 1/4″ |
| 35 mm | 1.3780″ | 1 3/8″ |
| 40 mm | 1.5748″ | 1 9/16″ |
| 45 mm | 1.7717″ | 1 25/32″ |
| 50 mm | 1.9685″ | 1 31/32″ |
| 60 mm | 2.3622″ | 2 3/8″ |
| 70 mm | 2.7559″ | 2 3/4″ |
| 75 mm | 2.9528″ | 2 15/16″ |
| 80 mm | 3.1496″ | 3 5/32″ |
| 90 mm | 3.5433″ | 3 17/32″ |
| 100 mm | 3.9370″ | 3 15/16″ |
| 150 mm | 5.9055″ | 5 29/32″ |
| 200 mm | 7.8740″ | 7 7/8″ |
| 250 mm | 9.8425″ | 9 27/32″ |
| 300 mm | 11.8110″ | 11 13/16″ |
| 400 mm | 15.7480″ | 15 3/4″ |
Metric to standard (SAE) sizes
Matching a metric socket or wrench to an SAE set? Here’s the closest standard fraction for each common size. Read “closest” literally — these are near misses, not equals. A 19 mm and a 3/4″ sit two-thousandths of an inch apart and swap fine. A 14 mm dropped onto a 9/16″ is looser, and on a tight bolt head that slack is how you round the corners off. Reach for the right size when the fit matters.
| Metric | Inches (decimal) | Closest SAE | Gap |
|---|---|---|---|
| 8 mm | 0.3150″ | 5/16″ | ±0.0025″ |
| 10 mm | 0.3937″ | 3/8″ | ±0.0187″ |
| 13 mm | 0.5118″ | 1/2″ | ±0.0118″ |
| 14 mm | 0.5512″ | 9/16″ | ±0.0113″ |
| 16 mm | 0.6299″ | 5/8″ | ±0.0049″ |
| 17 mm | 0.6693″ | 11/16″ | ±0.0182″ |
| 19 mm | 0.7480″ | 3/4″ | ±0.0020″ |
| 21 mm | 0.8268″ | 13/16″ | ±0.0143″ |
| 22 mm | 0.8661″ | 7/8″ | ±0.0089″ |
| 24 mm | 0.9449″ | 15/16″ | ±0.0074″ |
FAQ
How do I convert mm to inches?
Divide the millimeter value by 25.4. That’s the whole method. 16 mm ÷ 25.4 = 0.6299 in.
How many mm are in one inch?
25.4, exactly. It’s a defined value rather than a measurement, so there’s no rounding hiding inside the factor itself.
Is 25 mm exactly 1 inch?
No. 25 mm is 0.984 in — close enough that people round it in conversation, but a true inch is 25.4 mm. That 0.4 mm gap is small once, and it adds up fast the moment you stack a few inches together.
How do I get the answer as a fraction?
The converter shows it by default. By hand: take the decimal, multiply it by your denominator (16, 32, or 64), round to the nearest whole number — that’s your numerator. 7 mm = 0.2756 in; ×32 = 8.8 ≈ 9, so 9/32″.
Is the mm-to-inch conversion exact?
The factor is. 25.4 is exact, so the decimal is too. The fraction isn’t — it’s rounded to the nearest tick on whatever scale you chose, and the page states that precision next to the result.
