18 mm to Inches
Convert 18 millimeters to inches — instant, accurate, and easy
The Answer
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How to Convert 18 mm to Inches
To convert 18 millimeters to inches, divide the millimeter value by 25.4. This is because one inch equals exactly 25.4 millimeters — a standard defined by international agreement.
The Calculation
Applying the formula to 18 mm:
Result Summary for 18 mm
- Decimal inches: 0.7087″
- Fractional inches: 45/64″ (nearest 1/64)
- Feet and inches: 0 ft 0.71 in
18 mm Compared With 3/4 and 23/32 Inch
18 mm is approximately 0.7087 inches. The nearest 1/16-inch mark is 11/16 inch (17.4625 mm), 0.5375 mm below 18 mm.
3/4 inch is 19.05 mm, so it is 1.05 mm larger than 18 mm.
23/32 inch is 18.2562 mm, so it is 0.2562 mm larger than 18 mm.
Sheet goods are sold by nominal size. Metric 18 mm board is the usual substitute for 3/4-inch material, and US plywood sold as “3/4 inch” is often closer to 23/32 inch. Measure the actual sheet before cutting a groove to fit it.
Reference Table — Values Near 18 mm
| Millimeters | Decimal Inches | Fractional Inches |
|---|---|---|
| 15 mm | 0.5906″ | 19/32″ |
| 16 mm | 0.6299″ | 5/8″ |
| 17 mm | 0.6693″ | 43/64″ |
| 18 mm | 0.7087″ | 45/64″ |
| 19 mm | 0.7480″ | 3/4″ |
| 20 mm | 0.7874″ | 25/32″ |
| 21 mm | 0.8268″ | 53/64″ |
18 mm in Other Units
Millimeters convert cleanly into every other length unit. Here is 18 mm expressed seven different ways — useful when a drawing, spec sheet or supplier quotes a unit other than inches.
| Unit | 18 mm equals |
|---|---|
| Centimeters (cm) | 1.8 cm |
| Meters (m) | 0.018 m |
| Inches (in) | 0.7087 in |
| Feet (ft) | 0.0591 ft |
| Yards (yd) | 0.01969 yd |
| Thousandths of an inch (mil) | 708.7 mil |
| Typographic points (1/72 in) | 51.02 pt |
How Accurate Is Each Fraction of 18 mm?
18 mm equals 0.7087″ (rounded to four decimal places). Any fraction is a further rounding of the full-precision value, so each one carries a small error. This table shows the closest fraction at each common denominator and how far it actually sits from 18 mm.
| Rounded to | Fraction | Decimal | Fraction vs. original |
|---|---|---|---|
| Nearest 1/2″ | 1/2″ | 0.5000″ | −5.300 mm (below original) |
| Nearest 1/4″ | 3/4″ | 0.7500″ | +1.050 mm (above original) |
| Nearest 1/8″ | 3/4″ | 0.7500″ | +1.050 mm (above original) |
| Nearest 1/16″ | 11/16″ | 0.6875″ | −0.538 mm (below original) |
| Nearest 1/32″ | 23/32″ | 0.7188″ | +0.256 mm (above original) |
| Nearest 1/64″ | 45/64″ | 0.7031″ | −0.141 mm (below original) |
For woodworking, DIY and general workshop use, 45/64″ is the practical choice — it lands within 0.4 mm of 18 mm. For machining, toolmaking or CAD, use the decimal value 0.7087″ rather than any fraction.
FAQ About 18 mm to Inches
How many inches is 18 mm?
18 millimeters equals 0.7087 inches (rounded to 4 decimal places), or approximately 45/64″ (nearest 1/64 inch).
How accurate is the 18 mm to inches conversion?
The conversion of 18 mm to 0.7087 inches uses the exact definition 1 inch = 25.4 millimeters; the four-decimal result is rounded, so it is approximate.
Can I convert 18 mm to feet?
Yes. 18 millimeters equals approximately 0 ft 0.71 in.
📏 Need to measure 18mm accurately?
Digital calipers typically display readings to 0.01 mm resolution, enough to check 18 mm (≈ 0.7087″). See current options:
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