2/3 as a decimal
2/3 = 0.(6) (0.666667…) inches = 16.9333 mm.
0.(6)
2/3 of an inch — the bracketed digits repeat forever, so this form is exact where 0.666667… is not
Millimetres
16.9333 mm
Centimetres
1.69333 cm
Percent
66.6667%
Decimal
repeats
Where 2/3 falls at each precision, and whether the mark is the value exactly
| Rule | Nearest mark | Exact? |
|---|---|---|
| 1/16 | 11/16 | nearest |
| 1/32 | 21/32 | nearest |
| 1/64 | 43/64 | nearest |
Converting 2/3 to a decimal
A fraction is a division. 2/3 = 2 ÷ 3 = 0.(6) (0.666667…). The decimal repeats forever, written 0.(6) with the repeating digits bracketed. That happens because 3 factors into 3, which includes a prime other than 2 or 5 — so no power of ten is divisible by it and the long division never terminates.
In metric that is 16.9333 millimetres (1.69333 cm), since one inch is exactly 25.4 mm. As a percentage of an inch it is 66.6667%.
2/3 is not a mark on any imperial rule — the denominators on a rule are all powers of two, and 3 is not one. The nearest marks are 11/16 on a 1/16 rule, 21/32 on a 1/32 rule, 43/64 on a 1/64 rule, none of them exact.
Going the other way
To turn 0.666667 back into a fraction, pick the precision you are working to and multiply. At 1/16: 0.666667 × 16 = 10.6667, giving 11/16 after rounding to the nearest mark. At 1/32: 0.666667 × 32 = 21.3333, giving 21/32 after rounding to the nearest mark. At 1/64: 0.666667 × 64 = 42.6667, giving 43/64 after rounding to the nearest mark.
What is 2/3 as a decimal?
2/3 as a decimal is 0.(6) (0.666667…). Divide the numerator by the denominator: 2 ÷ 3 = 0.(6) (0.666667…). The division never comes out exactly, so the digits repeat.
What is 0.(6) (0.666667…) as a fraction?
0.666667… as a fraction is 2/3, in lowest terms.
How many millimetres is 2/3 of an inch?
2/3 of an inch is 16.9333 mm, or 1.69333 cm. An inch has been defined as exactly 25.4 mm since 1959, so this conversion is a definition rather than a measurement.
Where is 2/3 on a tape measure?
2/3 is not a mark on any imperial rule — the denominators on a rule are all powers of two, and 3 is not one. The nearest marks are 11/16 on a 1/16 rule, 21/32 on a 1/32 rule, 43/64 on a 1/64 rule, none of them exact.