What is 2/5 as a decimal?

2/5 is exactly 0.4 as a decimal.

How many millimetres is 2/5 of an inch?

2/5 of an inch is 10.16 mm, computed with the exact definition 1 inch = 25.4 mm.

2/5

Fraction2/5

Decimal0.4

Percent40%

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

Where the decimal comes from

2/5 equals 4/10 equals 0.4.

Multiply the top and bottom by 2 and the denominator becomes 10. A fraction over 10 is what a decimal is: 0.4 means 4 tenths.

40 of 100 squares — 0.4 of the whole. The same squares read as a percentage: 40%, because percent means per hundred.

Every way to write it

Decimal: 0.4
Percent: 40%
Ratio: 2 : 5 (part to whole)
As inches: 2/5″ = 10.16 mm

Equivalent fractions

Multiply the top and bottom of 2/5 by the same number and the value does not change:

2/5 = 4/10 = 6/15 = 8/20 = 10/25 = 12/30 · more, or pick a denominator

On the number line

As a measurement

Read as inches, 2/5″ is 10.16 mm exactly. The nearest marks on the finer rules:

Rule	Nearest mark	Decimal inches	mm	Difference
16ths	3/8″	0.375	9.525	−0.635 mm
32ths	13/32″	0.40625	10.3188	+0.1588 mm
64ths	13/32″	0.40625	10.3188	+0.1588 mm

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

Common questions

What is 2/5 as a decimal?: 2/5 is exactly 0.4 as a decimal.
What is 2/5 as a percentage?: 2/5 is exactly 40%.
How many millimetres is 2/5 of an inch?: 2/5 of an inch is 10.16 mm, computed with the exact definition 1 inch = 25.4 mm.

Fraction–decimal chartThe everyday set, printable.Rule charts16ths, 32nds, 64ths, 128ths.The rulerSee 2/5 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.

2/5