How to choose the base for a percentage calculation
Learn which number belongs in the denominator for percentage-of, ratio, and percentage-change questions.
Read guideUnderstand the base and formula
Percentage guides without hidden assumptions
Three focused guides explain how to choose the base, distinguish common comparison metrics, and reverse a known percentage change.
Percentage change vs percentage difference vs percentage points
Compare the three formulas, their required base, and why a percentage-point change needs the original rate before it can become a relative percent change.
Read guideHow to reverse a percentage increase or decrease
Recover an original value by dividing by the change multiplier instead of applying the opposite percentage.
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