Reduce a starting amount by a known percentage. Enter the two values below. The result panel shows the calculation used, and the examples explain how to interpret it.
How to use the percentage decrease calculator
- Identify the values required by the input labels.
- Enter percentages as whole-number rates: 15 means 15%.
- Select Calculate and read the result together with its formula.
- Check the assumptions below before applying the answer to a real situation.
Formula and method
Worked example
Reduce 480 by 12.5%. The reduction is 480 × 0.125 = 60. Subtract 60 to get 420. Equivalently, multiply by 0.875 because 87.5% of the original remains.
The percentage removed and the percentage remaining add to 100% for a reduction between 0% and 100%. A 30% reduction leaves 70%, so the multiplier is 0.70.
Repeated reductions
Two successive 10% reductions leave 0.90 × 0.90 = 0.81 of the original. A starting amount of 200 becomes 162, a total decrease of 19%. You cannot simply add the rates because the second base is smaller.
Example calculations
| Original | Decrease | New value |
|---|---|---|
| 200 | 15% | 170 |
| 100 | 25% | 75 |
| 80 | 50% | 40 |
| 60 | 100% | 0 |
Input rules and limitations
The mathematical mode accepts signed values and decreases above 100%, which can produce negative outputs. For ordinary sale prices use the discount calculator, which limits discounts to the realistic 0%–100% range.
Display precision can be changed from two to eight decimal places. Intermediate values are not rounded, but the calculation uses standard browser floating-point arithmetic. Currency figures should be rounded according to the rules relevant to your actual transaction.
Common questions
Does the result include units?
The calculator works with numbers. Keep the same units for comparable quantities and add the appropriate unit when reporting the result.
Why does the calculator reject some inputs?
The mathematical mode accepts signed values and decreases above 100%, which can produce negative outputs. For ordinary sale prices use the discount calculator, which limits discounts to the realistic 0%–100% range.
Is my information sent to a server?
Calculator values stay in your browser. They are not submitted to the website’s server for calculation.
Where can I learn the related formulas?
Use the main percentage calculator for basic shares and wholes, or browse our guides for worked examples and common mistakes.
Choose the right comparison
Use the percentage change calculator for an original-to-new comparison, the percentage difference calculator when neither value is the baseline, and the percentage points calculator to subtract rates. You can also return to the main percentage calculator.