Three everyday jobs: what is X% of Y, what percent is X of Y, and how much did a value go up or down. Type and read the answer.
"What's 15% off? How much is the tip? Did our traffic go up 12%?" Percentages show up in checkout lines, spreadsheets and group chats. This calculator answers the three questions people actually ask.
Tab one: X% of Y (the discount / the slice). Tab two: X is what percent of Y (the score, the share). Tab three: how much did something change (price up, users down). Switch tabs, type, done.
For shopping, budgeting, grading, sales — anywhere a number needs a percent sign — it saves you the mental math and the rounding errors.
Private and instant: computed in your browser, nothing logged. (Anonymous analytics only — privacy policy.)
Quick tip: the increase/decrease tab is signed. A negative result just means it went down — no separate "decrease" button needed.
Pick a tab (X% of Y / what % is X of Y / increase or decrease), enter the numbers, and the result updates live.