Is 21mm the same as 13/16?
In short: No. 21 millimeters is not equal to 13/16 of an inch. 21 mm is about 0.8268 inches, while 13/16 inch is 0.8125 inches, a difference of roughly 0.0143 inches (about 0.36 mm).
What 1316 means and how it relates to millimeters
1316 is a common shorthand for 13/16 of an inch, a fractional inch size widely used in machining, hardware, and manufacturing. To compare with metric sizes like 21 mm, it helps to convert between inches and millimeters using the standard: 1 inch = 25.4 millimeters.
Direct size comparison
To quantify how 21 mm compares to 13/16 inch, convert in both directions. The following conversions illustrate the difference.
- 21 mm = 0.8268 inches (21 ÷ 25.4).
- 0.8268 inches ≈ 0.827 inches when rounded to three decimals.
- For reference, 13/16 inch = 0.8125 inches.
Bottom line: 21 mm is not exactly 13/16 inch; it is larger by about 0.0143 inches (0.36 mm).
Converting 13/16 inch to millimeters
Similarly, converting 13/16 of an inch to millimeters shows the exact metric size you’re comparing against.
- 13/16 inch = 0.8125 inches.
- 0.8125 inches × 25.4 mm per inch = 20.6375 mm ≈ 20.64 mm.
- Thus, 13/16 inch is smaller than 21 mm by about 0.3625 mm (0.0143 inches).
In practical terms, the two measurements are close but not identical. When assembling parts, tolerances of a few hundredths of a millimeter can mean the difference between a snug fit and a loose one.
Summary
Ultimately, 21 mm and 1316 (13/16 in) are not the same dimension. 21 mm equals about 0.8268 inches (roughly 20.64 mm is the 13/16 inch metric equivalent), so the two values differ by roughly 0.36 mm. Always verify with precise measurements and consider manufacturing tolerances when selecting parts.
