Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate the percentage decrease between an original value and a new value.
This tool calculates the percentage decrease from an original value to a new (lower) value using ((original − new) ÷ original) × 100.
Enter the original value and the new value. The percentage decrease appears instantly.
Take a hypothetical laptop whose price drops from 800 to 620. Enter 800 as the original value and 620 as the new value. The drop is 180, and 180 divided by 800 is 0.225, so the tool shows 22.50% and labels it a Decrease. If you swap the two values, the result becomes -22.50% or a similar negative figure labelled Increase, because the tool measures how far the new value has fallen from the original.
decrease % = ((original - new) / |original|) x 100
The output is always rounded to two decimal places.
The most common use is finding how deep a discount really is. A shop shows a jacket at 90 that used to cost 120. The change is 30, and 30 divided by 120 is 25.00%, so the discount is 25%. To go the other way and find the sale price from a known percentage, multiply the original by one minus the percentage as a decimal: 120 x 0.75 = 90. You can enter 120 and 90 to check the result matches.
Because the base is the original value, a decrease and the increase needed to undo it are different percentages. A 20% drop from 100 leaves 80. To get back to 100 you need to grow by 20 on a base of 80, which is 25%. The same idea applies to investments, stock levels, and website traffic. If you want to work out the size of the rebound, run the new value and the original through the Percentage Increase Calculator.
The tool compares exactly two numbers. It does not handle a series of values, adjust for inflation, or work out annualised rates of decline. For medical, financial, tax or legal decisions, use the percentage as a quick estimate only and confirm important figures with your own records or a qualified professional. Typical uses include checking weight-loss progress as a share of starting weight in a general, non-medical sense, tracking reductions in expenses or energy use, and comparing test-score drops between two attempts.
The result will show as a negative percentage -- effectively a percentage increase. Use the Percentage Increase Calculator for that direction instead.
Enter the original price as the original value and the sale price as the new value. The result is the percentage taken off the original price.
It means the new value is zero, so the whole original amount has been lost or removed.
A negative result means the new value is higher than the original, so the quantity actually went up. The label beneath the number changes to Increase to make this clear.
No. The second drop applies to a smaller number, so together they make a 19% decrease. For example 100 becomes 90 and then 81.
Reference: NIST Weights and Measures