Discount calculator
Combine discounts, shipping and taxes and compare final prices.
FINANCEPercentage calculator
Calculate proportions, increases, decreases and changes between values.
Your starting point
Apply to prices, discounts and taxes
Your result
Editable example; you have not calculated your own inputs yet.
Result20
View full table · 1 rows
| Item | Value |
|---|---|
| Result | 20 |
Method and assumptions
Percentage of an amount: base × percentage / 100. Increases and decreases: base × (1 ± percentage / 100).
Change = (second value − base) / absolute base × 100. Ratio = second value / base × 100.
What if you change the plan?
Keep this result, change your inputs and compare.
Worked example and interpretation
20% of 150 is 150 × 20 / 100 = 30. Increasing 150 by 20% gives 180; reducing it by 20% gives 120. These are different operations on the same inputs. Going from 120 to 150 is (150 − 120) / 120 × 100 = 25%.
What to check
Percentages depend on the base. A 20% rise followed by a 20% fall does not restore the original amount: 100 → 120 → 96. Rates of 4% and 5% differ by 1 percentage point, but the relative increase is 25%.
Frequently asked questions
How do I calculate X% of an amount?
Multiply the amount by X and divide by 100. For example, 15% of 200 is 200 × 15 / 100 = 30. Enter the amount and percentage in the corresponding mode.
What percentage of B is A?
Divide A by B and multiply by 100; B must not be zero. For example, 30 is 15% of 200. This is different from calculating how much an amount has changed.
What is the difference between percent and percentage points?
Moving from 20% to 25% is an increase of 5 percentage points. The relative increase is 25%, since (25 − 20) / 20 × 100 = 25. State which measure you are comparing.
How do I calculate a percentage increase or decrease?
For a positive starting value, use (final − initial) / initial × 100. From 80 to 100 is a 25% increase; from 100 to 80 is a 20% decrease. This relative change is undefined for a zero starting value.
Why does adding then subtracting 20% not restore the original?
Each percentage uses a different base. Increasing 100 by 20% gives 120; reducing that new amount by 20% gives 96. The final loss relative to 100 is 4%.