How each calculation works
"What is X% of Y" multiplies Y by X divided by 100. "X is what percent of Y" divides X by Y and multiplies by 100. Percentage increase or decrease takes the difference between two numbers, divides it by the original number, and multiplies by 100 — a positive result means an increase, a negative result means a decrease.
Where this comes up
Percentage math shows up constantly in everyday decisions: figuring out a discount at checkout, calculating a tip, comparing exam or grade scores, tracking a pay raise, or working out the return on an investment. Because small errors compound quickly with percentages, it's worth double-checking by hand-calculator rather than estimating.
Frequently asked questions
Which calculator do I use to figure out a discount at checkout?
Use 'What is X% of Y' with the discount percentage and the original price to find how much you save, or use the Discount Calculator tool for a version built specifically around sale prices.
How do I calculate a percentage increase, like a salary raise?
Use the third calculator, 'Percentage increase / decrease,' entering your old salary as the first number and your new salary as the second. A positive result is the percentage increase; a negative result would indicate a decrease.
Can I use negative numbers?
Yes, all three calculators accept negative numbers and will calculate correctly, though negative inputs are uncommon outside of specific financial or scientific contexts.
Are the results rounded?
Results are rounded to two decimal places for readability. For most everyday use — shopping, grades, tips — this level of precision is more than sufficient.