What is 1/2 as a decimal?

1/2 is exactly 0.5 as a decimal.

How many millimetres is 1/2 of an inch?

1/2 of an inch is 12.7 mm, computed with the exact definition 1 inch = 25.4 mm.

1/2

Fraction1/2

Decimal0.5

Percent50%

1 of 2 equal parts filled — the same share as a bar and as a circle.

Where the decimal comes from

1/2 equals 5/10 equals 0.5.

Multiply the top and bottom by 5 and the denominator becomes 10. A fraction over 10 is what a decimal is: 0.5 means 5 tenths.

50 of 100 squares — 0.5 of the whole. The same squares read as a percentage: 50%, because percent means per hundred.

Every way to write it

Decimal: 0.5
Percent: 50%
Ratio: 1 : 2 (part to whole)
As inches: 1/2″ = 12.7 mm

Equivalent fractions

Multiply the top and bottom of 1/2 by the same number and the value does not change:

1/2 = 2/4 = 3/6 = 4/8 = 5/10 = 6/12 · more, or pick a denominator

On the number line

As a measurement

Read as inches, 1/2″ is 12.7 mm exactly. The nearest marks on the finer rules:

Rule	Nearest mark	Decimal inches	mm	Difference
16ths	1/2″	0.5	12.7	exact
32ths	1/2″	0.5	12.7	exact
64ths	1/2″	0.5	12.7	exact

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

Common questions

What is 1/2 as a decimal?: 1/2 is exactly 0.5 as a decimal.
What is 1/2 as a percentage?: 1/2 is exactly 50%.
How many millimetres is 1/2 of an inch?: 1/2 of an inch is 12.7 mm, computed with the exact definition 1 inch = 25.4 mm.

Fraction–decimal chartThe everyday set, printable.Rule charts16ths, 32nds, 64ths, 128ths.The rulerSee 1/2 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.

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