What is 0.66 as a fraction?

0.66 as a fraction is 33/50. Write the digits over 100 to get 66/100, then divide top and bottom by 2.

What is 0.66 as a percentage?

0.66 is 66%. Multiplying a decimal by 100 moves the point two places to the right.

How many millimetres is 0.66 of an inch?

0.66 inches is 16.764 mm, using the exact definition 1 inch = 25.4 mm.

0.66 as a fraction

Fraction33/50lowest terms

Decimal0.66

Percent66%

How to get there

0.66 has 2 digits after the point, so it is that many hundredths: write the digits over 100 — 66/100.
66 and 100 share a greatest common divisor of 2. Divide both by it: 33/50.

66 of 100 squares — 0.66 of the whole, which is also 66%.

As a measurement

Read as inches, 0.66″ is 16.764 mm exactly. The nearest marks on a rule:

Rule	Nearest mark	Inches	mm	Difference
16ths	11/16″	0.6875	17.4625	+0.6985 mm
32ths	21/32″	0.65625	16.6688	−0.0953 mm
64ths	21/32″	0.65625	16.6688	−0.0953 mm

Common questions

What is 0.66 as a fraction?: 0.66 as a fraction is 33/50. Write the digits over 100 to get 66/100, then divide top and bottom by 2.
What is 0.66 as a percentage?: 0.66 is 66%. Multiplying a decimal by 100 moves the point two places to the right.
How many millimetres is 0.66 of an inch?: 0.66 inches is 16.764 mm, using the exact definition 1 inch = 25.4 mm.

The same number, other ways

33/50Everything about the fraction: equivalents, the bar model, the number line.66%The same value as a percentage, with its own derivation.Decimal → fraction chartThe whole lookup table, printable.Nearest fractionMatch 0.66″ against any rule, with the exact error.

Where this comes from. Exact rational arithmetic on the values shown — fractions are pairs of integers until display, and inch–metric conversion uses 25.4 mm to the inch, exact by definition since 1959. See the full methodology.