Scientific calculator

How to write a calculation

Write the whole expression on one line, the way you would read it out loud, then press Enter or the button. Brackets work, the keypad above works, and so do symbols copied from a document (× ÷ · − √ π ² ³), while a colon counts as a division, so 6:2 gives 3. The decimal separator is the point, and the thousands separator must never be typed: if you write 1,500 the calculator stops and tells you, because nobody can guess what you meant.

Precedence, and the line that shows how it was read

The usual order applies: brackets first, then powers, then multiplication and division, then addition and subtraction. Two details that start arguments online: powers group from the right, so 2^3^2 is 512 and not 64, and a minus sign in front of a power is applied afterwards, so -2^2 is -4. Implied multiplication (2π, 3(4+1)) has exactly the same precedence as the written one, so 1/2π is half of pi. That is why a «Read as» line always appears under the result, rewriting your calculation with the real brackets: if it says something different from what you had in mind, the problem is in the expression, not in the answer.

Degrees or radians, and why sin(π) is not zero

The menu at the top decides how sin, cos and tan read their angle and which unit asin, acos and atan give back; whenever a calculation contains an angle the result reminds you of the setting. In degrees the calculator recognises the exact values, so sin(180) returns a clean 0 and tan(90) says the tangent does not exist instead of printing a huge number. In radians that is impossible: π cannot be represented in binary, so sin(pi) returns 1.22e-16, which is zero plus the rounding error of the machine. The hyperbolic functions sinh, cosh and tanh always work on a plain number rather than an angle, and the menu leaves them alone.

Percent, factorial, remainder and memory

The % sign always divides by one hundred, with no hidden rules: 15% is 0.15 and 200*15% gives 30. To add 15% to a price write 200*1.15, to take it off write 200*0.85. This is a deliberate choice, because the behaviour of the «plus percent» key changes from calculator to calculator and gives different answers to the same question. The exclamation mark is the factorial and works on whole numbers from 0 to 170, the point where the result no longer fits in a number. The mod operator returns the remainder with the sign of the divisor, so 17 mod 5 is 2 and -1 mod 5 is 4. M+ and M− add and subtract the current value to the memory, MR puts it back into the expression, and you can also type ans for the last result and mem for the memory.

Precision, limits and privacy

Everything runs on the floating point numbers of the browser, which hold about 15 significant digits, so the result is displayed rounded to the twelfth digit, otherwise 0.1+0.2 would show up as 0.30000000000000004. The full value is still kept in ans, in the memory and in the history, so chaining calculations does not make the approximation worse; above fifteen digits the display switches to scientific notation, where the extra digits would be made up. This is a numeric calculator: it does not solve equations with an x in them, it does not differentiate or integrate, and it has no complex numbers, so the square root of a negative number is reported as an error instead of an imaginary value. Every calculation happens inside your browser, nothing is sent to a server, and the history lives only in this tab: close it and it is gone.