Find the percentage decrease between two numbers, or decrease a number by any percentage. Enter the starting value first. Free, private, and runs entirely in your browser.
The percentage decrease is the change divided by the starting value, times 100. To decrease a number by a percentage, multiply it by 1 minus the percentage written as a decimal.
How do I calculate a percentage decrease? Subtract the new value from the old one, divide by the old value and multiply by 100. From 100 to 80 that is 20%.
Why does the starting value matter? The same change is a different percentage depending on the base. A rise from 80 to 100 is 25%, but a fall from 100 to 80 is only 20%.
A price falls from $100 to $80. The change is 100 − 80 = 20, and 20 ÷ 100 = 0.20, so the decrease is 20%. To decrease $100 by 20% instead, compute 100 × 0.80 = $80.
Can the result be more than 100%? An increase can be any size, since a value can more than double. A decrease cannot exceed 100% for positive numbers.
What if the starting value is zero? A percentage change from zero is undefined, because you cannot divide by zero.
The word percent comes from the Latin per centum, meaning by the hundred. The % symbol evolved from handwritten abbreviations of the Italian per cento between the 15th and 17th centuries. Percentages made it easy to compare quantities of different sizes, which is why they became standard in trade, taxes and interest.
Use this calculator for discounts, price drops, falling sales or weight loss measured against a start value. A price that drops from $250 to $200 fell by 20%. Switch to the second mode to apply a known percentage, such as a 15% discount on $80, which leaves $68.
How do I find the percent difference between two values? Divide the absolute difference by the average of the two values when neither is the clear starting point.
How do I decrease by a percentage in a spreadsheet? Use =A1*(1-B1) with the percentage stored as a decimal or a percent-formatted cell.