What is 0.3 as a fraction?

0.3 as a fraction is 3/10. The digits go over 10, and 3 and 10 share no common factor, so it is already in lowest terms.

What is 0.3 as a percentage?

0.3 is 30%. Multiplying a decimal by 100 moves the point two places to the right.

How many millimetres is 0.3 of an inch?

0.3 inches is 7.62 mm, using the exact definition 1 inch = 25.4 mm.

0.3 as a fraction

Fraction3/10lowest terms

Decimal0.3

Percent30%

How to get there

0.3 has 1 digit after the point, so it is that many tenths: write the digits over 10 — 3/10.
3 and 10 share no factor but 1, so 3/10 is already in lowest terms.

30 of 100 squares — 0.3 of the whole, which is also 30%.

As a measurement

Read as inches, 0.3″ is 7.62 mm exactly. The nearest marks on a rule:

Rule	Nearest mark	Inches	mm	Difference
16ths	5/16″	0.3125	7.9375	+0.3175 mm
32ths	5/16″	0.3125	7.9375	+0.3175 mm
64ths	19/64″	0.296875	7.5406	−0.0794 mm

Common questions

What is 0.3 as a fraction?: 0.3 as a fraction is 3/10. The digits go over 10, and 3 and 10 share no common factor, so it is already in lowest terms.
What is 0.3 as a percentage?: 0.3 is 30%. Multiplying a decimal by 100 moves the point two places to the right.
How many millimetres is 0.3 of an inch?: 0.3 inches is 7.62 mm, using the exact definition 1 inch = 25.4 mm.

The same number, other ways

3/10Everything about the fraction: equivalents, the bar model, the number line.30%The same value as a percentage, with its own derivation.Decimal → fraction chartThe whole lookup table, printable.Nearest fractionMatch 0.3″ 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.