Percentage decrease from 100 to 80
From 100 to 80 is a 20% decrease.
Example answer
-20%
From 100 to 80 is a 20% decrease.
Display up to your selected decimal places. Browser arithmetic is used.
See the calculation
80 − 100 = -20; -20 ÷ 100 × 100 = -20%
Worked example with the original numbers
How to calculate this answer
(New − original) ÷ original × 100
- 80 − 100 = -20
- -20 ÷ 100 × 100 = -20%
Check: 100 × (1 + (-20) ÷ 100) = 80
A quick way to check it
The amount falls by 20. Divide that fall by the original 100 to get a 20% decrease.
What the numbers mean
A price reduction from 100 to 80 is a 20% decrease. Returning from 80 to 100 requires a 25% increase, not 20%.
A mistake to avoid
Divide the change by the original value. Swapping the values changes the baseline, so the reverse rate is different.
Related calculations to try
Use the percentage calculator for a different type of question, apply one percentage to a list, or compare several percentage rates.
Questions about this example
Percentage decrease from 100 to 80
From 100 to 80 is a 20% decrease. The amount falls by 20. Divide that fall by the original 100 to get a 20% decrease.
Can I change the numbers?
Yes. Edit the two inputs to see a new answer, or use Calculate. Reset example restores this page’s starting numbers. The worked explanation below the calculator continues to describe the original example.
Why might another answer look slightly different?
Decimal settings affect display rounding. A ≈ sign marks a rounded result, and very small values may round to zero. This tool uses ordinary browser arithmetic rather than exact decimal arithmetic. Check the formula and baseline before comparing results.
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