55/64 Inch to MM
Fractional inch to millimeters
55/64 inch (55/64β³)
21.828125 mm
= 2.182812 cm Β· 0.859375 inch decimal Β· 1 inch = 25.4 mm exactly
π‘ Standard fractional drill bit size. 1/64 in is also the finest graduation printed on a US tape measure.
Also written as
55/64 to mm Β· 55/64 in mm Β· 55/64" in mm Β· 55/64 inch in mm Β· 55/64 inches to millimeters Β· 55/64 en mm Β· 0.859375 inch to mm
All of these mean the same measurement. The double-prime mark (β³) 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
22 mm
55/64β³ = 21.828125 mm Β· difference 0.1719 mm
Metric drills step in 0.5 mm, so a fractional inch size rarely lands exactly on one. A 0.1719 mm gap is usually invisible in a clearance hole but changes the fit on a press fit or a tapped hole.
Nearby fractional inches
| Fraction | mm | cm | Decimal |
|---|---|---|---|
| 53/64β³ | 21.034375 mm | 2.103438 cm | 0.828125β³ |
| 27/32β³ | 21.43125 mm | 2.143125 cm | 0.84375β³ |
| 55/64β³ | 21.828125 mm | 2.182812 cm | 0.859375β³ |
| 7/8β³ | 22.225 mm | 2.2225 cm | 0.875β³ |
| 57/64β³ | 22.621875 mm | 2.262188 cm | 0.890625β³ |
55/64β³ is 55/64 of an inch β the 55th mark from zero on a tape measure graduated in sixty-fourths.
FAQ
How many mm is 55/64 inch?
55/64 inch equals 21.828125 mm. One inch is defined as exactly 25.4 mm, so the result is 25.4 Γ 55 Γ· 64.
What is 55/64 inch in decimal?
55/64 inch is 0.859375 inch in decimal, which is 21.828125 mm or 2.182812 cm.
Which metric size is closest to 55/64 inch?
22 mm is the closest common metric size, a difference of 0.1719 mm. Fractional-inch and metric fasteners are not interchangeable when the gap is more than about 0.2 mm.
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.
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