No mode switching required. Each calculator runs independently so you can solve multiple problems at once.
What is X% of Y?
Result
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X is what % of Y?
Percent
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% change from → to
increase
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Add / subtract %
New value (—)
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Practical tips & common mistakes
Stack discounts correctly
A 20% store discount plus 10% coupon is not 30% off — apply each percent to the remaining balance in sequence.
Adding percents blindly
Raising a price 15% then lowering 15% does not return to the original number. Percent change is always relative to the current value.
Quick mental math
10% is easy: move the decimal left once. For 15%, find 10% + half of 10%. Use this calculator to verify bill splits and tip math.
When this matters
Sales tax, markups, commission, grade curves, and fitness progress all use the same four percentage patterns this page covers.