What are the must-know fraction ↔ percentage conversions?

Question

Accepted Answer

Memorise the halves, quarters, eighths, thirds, fifths — they turn percentage problems into easy fraction ones.

Fraction
%

1/2
50

1/8
12.5

1/4
25

3/8
37.5

3/4
75

5/8
62.5

1/5
20

1/3
33.3̅

1/10
10

2/3
66.6̅

So "37.5% of 240" is just 3/8 of 240 = 90, and "a third off" is knocking off 33.3%.

Fraction	%	Fraction	%
1/2	50	1/8	12.5
1/4	25	3/8	37.5
3/4	75	5/8	62.5
1/5	20	1/3	33.3̅
1/10	10	2/3	66.6̅