What is 0.8 as a fraction?

0.8 as a fraction is 4/5. Write the digits over 10 to get 8/10, then divide top and bottom by 2.

What is 0.8 as a percentage?

0.8 is 80%. Multiplying a decimal by 100 moves the point two places to the right.

How many millimetres is 0.8 of an inch?

0.8 inches is 20.32 mm, using the exact definition 1 inch = 25.4 mm.

0.8 as a fraction

Fraction4/5lowest terms

Decimal0.8

Percent80%

How to get there

0.8 has 1 digit after the point, so it is that many tenths: write the digits over 10 — 8/10.
8 and 10 share a greatest common divisor of 2. Divide both by it: 4/5.

80 of 100 squares — 0.8 of the whole, which is also 80%.

As a measurement

Read as inches, 0.8″ is 20.32 mm exactly. The nearest marks on a rule:

Rule	Nearest mark	Inches	mm	Difference
16ths	13/16″	0.8125	20.6375	+0.3175 mm
32ths	13/16″	0.8125	20.6375	+0.3175 mm
64ths	51/64″	0.796875	20.2406	−0.0794 mm

Common questions

What is 0.8 as a fraction?: 0.8 as a fraction is 4/5. Write the digits over 10 to get 8/10, then divide top and bottom by 2.
What is 0.8 as a percentage?: 0.8 is 80%. Multiplying a decimal by 100 moves the point two places to the right.
How many millimetres is 0.8 of an inch?: 0.8 inches is 20.32 mm, using the exact definition 1 inch = 25.4 mm.

The same number, other ways

4/5Everything about the fraction: equivalents, the bar model, the number line.80%The same value as a percentage, with its own derivation.Decimal → fraction chartThe whole lookup table, printable.Nearest fractionMatch 0.8″ 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.