What is 1/5 as a decimal?

1/5 is exactly 0.2 as a decimal.

How many millimetres is 1/5 of an inch?

1/5 of an inch is 5.08 mm, computed with the exact definition 1 inch = 25.4 mm.

1/5

Fraction1/5

Decimal0.2

Percent20%

1 of 5 equal parts filled — the same share as a bar and as a circle.

Where the decimal comes from

1/5 equals 2/10 equals 0.2.

Multiply the top and bottom by 2 and the denominator becomes 10. A fraction over 10 is what a decimal is: 0.2 means 2 tenths.

20 of 100 squares — 0.2 of the whole. The same squares read as a percentage: 20%, because percent means per hundred.

Every way to write it

Decimal: 0.2
Percent: 20%
Ratio: 1 : 5 (part to whole)
As inches: 1/5″ = 5.08 mm

Equivalent fractions

Multiply the top and bottom of 1/5 by the same number and the value does not change:

1/5 = 2/10 = 3/15 = 4/20 = 5/25 = 6/30 · more, or pick a denominator

On the number line

As a measurement

Read as inches, 1/5″ is 5.08 mm exactly. The nearest marks on the finer rules:

Rule	Nearest mark	Decimal inches	mm	Difference
16ths	3/16″	0.1875	4.7625	−0.3175 mm
32ths	3/16″	0.1875	4.7625	−0.3175 mm
64ths	13/64″	0.203125	5.1594	+0.0794 mm

Need a different rule or a tolerance? Nearest fraction · Within tolerance

Common questions

What is 1/5 as a decimal?: 1/5 is exactly 0.2 as a decimal.
What is 1/5 as a percentage?: 1/5 is exactly 20%.
How many millimetres is 1/5 of an inch?: 1/5 of an inch is 5.08 mm, computed with the exact definition 1 inch = 25.4 mm.

Fraction–decimal chartThe everyday set, printable.Rule charts16ths, 32nds, 64ths, 128ths.The rulerSee 1/5 in its place.

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.

1/5