Percent Adjustment Calculator
A percent adjustment runs three ways, and this tool does all three. Find the percent: what percent is a $15 change on $200? Apply a percent: what is $500 after a 12% increase? Find the original: what was the price before a 15% discount left $42.50? Pick a mode and enter two numbers.
Worked examples, checked against this exact tool
Find the percent: a $15 rise on $200 is a 7.50% increase. Apply a percent: $500 plus 12% is $560.00; $50 with a 15% discount is $42.50. Find the original: $42.50 after a 15% discount means the original was $50.00.
The formulas
Find the percent: adjustment ÷ original × 100. Apply a percent: original × (1 + percent ÷ 100); use a negative percent for discounts. Find the original: adjusted ÷ (1 + percent ÷ 100).
Percentage points vs percent change
Going from 20% to 25% is a 5 percentage point rise but a 25% percent increase (5 ÷ 20). Mixing these up is the most common percent-adjustment error in reports: name which one you mean.
Chained adjustments do not add
A 8% rise followed by a 5% fall is not a 3% rise: 1.08 × 0.95 = 1.026, a 2.60% overall increase. Apply them one at a time with the “apply a percent” mode, chaining the output into the next input.
What competing calculators miss
The best-known percent-adjustment tools each handle one direction: either “what percent is this change” or “apply this percent.” None runs the reverse (“what was the original before the discount”). This page does all three in one place with the formula shown for each.
Frequently asked questions
How do you calculate a percent adjustment?
Divide the adjustment by the original and multiply by 100. $15 ÷ $200 × 100 = 7.5%.
How do you apply a percent increase to a price?
Multiply by (1 + percent/100). $500 × 1.12 = $560.00.
How do you apply a percent discount?
Use a negative percent: $50 × (1 − 0.15) = $42.50.
How do you find the original price before a discount?
Divide the sale price by (1 − discount). $42.50 ÷ 0.85 = $50.00.
What is the difference between percent change and percentage points?
Percent change is relative to the starting value; percentage points are the plain arithmetic difference between two percentages.
Why do chained percentages not add up?
Each applies to a new base. +8% then −5% is 1.08 × 0.95 = +2.6%, not +3%.
Can the adjustment be negative?
Yes. A negative adjustment amount gives a negative percent: a decrease.
What if the original value is zero?
The percent is undefined (division by zero): the tool will tell you rather than invent a number.
How do I reverse a percent increase?
Use the “find the original” mode: divide by (1 + percent/100), not subtract the percent.
Is a 50% increase then 50% decrease back to start?
No: 1.5 × 0.5 = 0.75, so you end 25% below where you started.