What is 0.21 as a fraction?

0.21 as a fraction is 21/100. The digits go over 100, and 21 and 100 share no common factor, so it is already in lowest terms.

What is 0.21 as a percentage?

0.21 is 21%. Multiplying a decimal by 100 moves the point two places to the right.

How many millimetres is 0.21 of an inch?

0.21 inches is 5.334 mm, using the exact definition 1 inch = 25.4 mm.

0.21 as a fraction

Fraction21/100lowest terms

Decimal0.21

Percent21%

How to get there

0.21 has 2 digits after the point, so it is that many hundredths: write the digits over 100 — 21/100.
21 and 100 share no factor but 1, so 21/100 is already in lowest terms.

21 of 100 squares — 0.21 of the whole, which is also 21%.

As a measurement

Read as inches, 0.21″ is 5.334 mm exactly. The nearest marks on a rule:

Rule	Nearest mark	Inches	mm	Difference
16ths	3/16″	0.1875	4.7625	−0.5715 mm
32ths	7/32″	0.21875	5.5563	+0.2223 mm
64ths	13/64″	0.203125	5.1594	−0.1746 mm

Common questions

What is 0.21 as a fraction?: 0.21 as a fraction is 21/100. The digits go over 100, and 21 and 100 share no common factor, so it is already in lowest terms.
What is 0.21 as a percentage?: 0.21 is 21%. Multiplying a decimal by 100 moves the point two places to the right.
How many millimetres is 0.21 of an inch?: 0.21 inches is 5.334 mm, using the exact definition 1 inch = 25.4 mm.

The same number, other ways

21/100Everything about the fraction: equivalents, the bar model, the number line.21%The same value as a percentage, with its own derivation.Decimal → fraction chartThe whole lookup table, printable.Nearest fractionMatch 0.21″ 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.