Percentage Calculator not working? Here's how to fix it
Most issues with the Percentage Calculator are small and fixable in seconds. Work through these in order.
1. The result is 100 times too large or too small
You likely entered a decimal instead of a percent, or vice versa. For 15%, enter 15, not 0.15. For a value of 0.5, that's 50%, not 0.5%. Enter the number with the units the field expects.
2. You used the wrong mode
Percent of, What percent, and Percent change solve different problems. If the answer seems wrong, confirm you picked the mode for what you're trying to find — for example, use What percent to express one number relative to another, not Percent of.
3. Percent change looks larger than expected
Percent change is relative to the old value, so a change from 40 to 50 is 25%, not 10%. Make sure you put the correct value in the old and new fields — swapping them changes both the sign and possibly the magnitude.
4. The sign of the result is wrong
For a decrease, percent change is negative. If your increase shows negative, check that the new value is actually larger than the old value, and that you didn't swap the fields.
5. The tool won't load at all
Reload the page or open it in a fresh tab. If an extension blocks scripts, try private (incognito) mode — the calculator needs JavaScript, which is on by default in every modern browser.
Still stuck?
Try a different current browser (Chrome, Firefox, Safari, Edge). The tool behaves the same everywhere, so a fresh environment usually resolves the last edge cases.
Verdict
Most problems with Percentage Calculator are solved by entering the right mode, correct decimal-vs-percent value, and ordered change values.