Question 1

How do I calculate a percentage of any number (What is P% of X)?

Accepted Answer

Convert the percentage into a decimal by dividing by 100, then multiply by the base number. Formula: Result = (P / 100) × X. For example, 15% of 240 is 0.15 × 240 = 36.

Question 2

How do I calculate percentage change or growth between two numbers?

Accepted Answer

Subtract the starting value from the ending value, divide the difference by the starting value, and multiply by 100: Percentage Change = ((Y - X) / |X|) × 100. A positive outcome indicates percentage increase, while a negative outcome represents a decrease.

Question 3

What is Reverse Percentage and how do I back out sales tax or discounts?

Accepted Answer

Reverse percentage reconstructs the original pre-adjusted value. If a price of $108 includes an 8% sales tax, the original pre-tax value is $108 / (1 + 0.08) = $100. If an item costs $80 after a 20% discount, the original price was $80 / (1 - 0.20) = $100.

Question 4

What is Percentage Difference and how is it distinct from Percentage Change?

Accepted Answer

Percentage Difference measures the symmetric relative spread between two numbers when neither is considered a starting "baseline." It divides the absolute difference by the average of the two numbers: (|X - Y| / ((X + Y) / 2)) × 100.

Question 5

What is the difference between a Percentage and a Percentage Point?

Accepted Answer

A percentage represents a relative proportion (e.g. sales increased by 10%). A percentage point represents the simple arithmetic difference between two percentages (e.g. an interest rate rising from 5% to 7% is an increase of 2 percentage points, but a 40% relative increase).

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