13/16 Inch to MM
Fractional inch to millimeters
13/16 inch (13/16″)
20.6375 mm
= 2.0637 cm · 1 inch = 25.4 mm exactly
💡 Commonly used for spark plug sockets, hex bolt heads.
Nearby fractional inches
| Fraction | mm | cm |
|---|---|---|
| 11/16″ | 17.4625 mm | 1.7462 cm |
| 3/4″ | 19.05 mm | 1.905 cm |
| 13/16″ | 20.6375 mm | 2.0637 cm |
| 7/8″ | 22.225 mm | 2.2225 cm |
| 15/16″ | 23.8125 mm | 2.3813 cm |
Also written as
13/16 to mm · 13/16 in mm · 13/16" in mm · 13/16 inch in mm · 13/16 inches to millimeters · 13/16 en mm · 0.8125 inch to mm
All of these mean the same measurement. The double-prime mark (″) and the plain quote (") both stand for inches, and en mm is simply the French and Spanish wording of the same question.
Closest metric drill size
21 mm
13/16″ = 20.6375 mm · difference 0.3625 mm
Metric drills step in 0.5 mm, so a fractional inch size rarely lands exactly on one. A 0.3625 mm gap is usually invisible in a clearance hole but changes the fit on a press fit or a tapped hole.
FAQ
How many mm is 13/16 inch?
13/16 inch equals 20.6375 mm. Since one inch is defined as exactly 25.4 mm, the result is 25.4 × 13 ÷ 16.
Why is the value exact?
The international yard and pound agreement of 1959 fixed the inch at exactly 25.4 mm, so fractional inch conversions terminate rather than repeat.