Percentage Calculator and Rule of Three
Solve the most common percentage calculations and the simple rule of three. The result appears automatically.
What is X% of a value?
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of
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X is what percent of Y?
value
is what % of
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Percentage change (increase/decrease)
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to
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Simple rule of three
If A is to B, then C is to X.
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B
C
X
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Frequently asked questions
How do you calculate the percentage of a value?
Multiply the value by the percentage and divide by 100. Example: 10% of 250 = 250 × 10 ÷ 100 = 25.
How does the simple rule of three work?
With three known values (A, B and C), we find the fourth (X) by proportion: X = (B × C) ÷ A.
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