How it works

The calculator

The keypad is laid out like a desk calculator. Memory keys run along the top. The keys that change the number you are typing sit above the digits, and the operators, percent and square root sit on the right, with a large equals key at the bottom. The small line at the top of the display shows the sum you are building; the large number underneath is the number you are typing or the latest answer.

• Order of operations. Multiplication and division are worked out before addition and subtraction, left to right, so 2 + 3 × 4 is 14. Why that matters.
• Changing your mind. Press a different operator straight after another and it replaces the first one: 5 + × becomes 5 ×.
• Decimals. A number can only have one decimal point; extra presses are ignored.
• Tidy results. Answers are rounded to 12 significant digits, so 0.1 + 0.2 shows 0.3 rather than computer rounding noise.
• Dividing by zero shows “Error”. Press any digit or AC to start again.

The extra keys

• Percent (%). Works the way handheld calculators do. After + or −, it takes that percentage of the total so far: 200 + 10% adds 10% of 200, giving 220. After × or ÷, it divides by 100 first, so 200 × 10% is 20. On its own, 10% is 0.1.
• Square root (√). Works straight away on the number in the display: type 16, press √ and you see 4. Your step records it as √16. A negative number has no square root, so the display says so; press any key to carry on.
• Change sign (±). Makes the number you are typing negative, or positive again. Press it after equals to flip the answer and keep going from there.
• C and AC. While you are typing a number, the key reads C and clears just that number, so 12 + 35 goes back to 12 + and you can type the right one. Otherwise it reads AC and clears the whole sum. Neither touches your steps or memory.
• Memory (MC, MR, M+, M−). M+ adds the number in the display to memory and M− takes it away. MR brings the stored number into your sum, and MC sets memory back to zero. A small M in the display shows when memory holds something. Memory is kept in your browser, like your steps.

Copying answers

Each time you press equals, the answer is copied to your clipboard, ready to paste into a spreadsheet, email or form. The display confirms it, for example “Copied 220 to clipboard”. The number is copied without thousands separators, and errors are never copied.

To keep your clipboard as it is, turn off the switch under the keypad; the setting is remembered. The site only ever writes to your clipboard and never reads what is on it. If your browser blocks copying, the display tells you, and you can select the number and copy it yourself.

Your steps

Every time you press equals, the calculation and its answer are added to the “Your steps” panel as the next numbered step, for example 12 × 3 = 36. Calculations that end in an error are not recorded.

To go back, tap or click any step. Three things happen:

1. That step’s answer goes back into the display, and the top line tells you which step it came from.
2. The step is highlighted in the list so you can see where you are.
3. Your next key carries on from that answer. Press an operator to keep building on it, or a digit to start a fresh sum.

Nothing is deleted when you go back. Later steps stay in the list, and any new calculation is added to the end, so you can compare different routes through the same problem. Our bill-splitting example shows this in practice.

Keyboard shortcuts

Where your history lives

Your steps, memory and copy setting are saved in your browser’s local storage on your own device, so they are still there if you reload the page or come back later. They are never sent to us. Use Clear history under the list to remove them, or clear your browser’s site data. In a private or incognito window, history lasts only until you close it. Read more in our privacy policy.