Smart calculator
Type an expression and read the answer live, with percentages the way people mean them.
Questions
What does this tool do?
The Smart calculator is a calculator without a keypad: type an expression — 1250 − 15%, 340 × 12, (450 + 270) / 3, 2^10, sqrt(2) — and the answer appears under it as you type. Percentages work the way people mean them, and the session's calculations stay in a history you can pick up again.
How do percentages work?
1250 − 15% takes fifteen percent off: 1 062.5. 200 + 15% adds it: 230. 340 × 12% is twelve percent of 340: 40.8. 50 ÷ 10% is 500. A percentage on its own is a fraction: 15% is 0.15.
What can I type?
Plus, minus, times (× or *), divided by (÷ or /), power (^), percent (%), brackets, a minus in front of a number, and the functions sqrt, abs and round. A comma or a dot as the decimal mark; spaces inside big numbers are fine.
Which keys does it understand?
Enter keeps the line in the history. The up and down arrows walk through earlier lines. Escape clears the field. Each history row has its own Copy.
How precise is it?
Fifteen significant digits, the most a double can carry reliably; 0.1 + 0.2 comes out as 0.3, not 0.30000000000000004.
Where does the history live?
In this browser tab only. It survives a reload, goes when the tab closes, and Clear history empties it now.