Online Calculator

Two layouts, one engine

Basic and Scientific are two key arrangements over the same arithmetic, so a value left on the display survives the switch. Basic covers the four operations plus square root, square, percentage and memory. Scientific adds cube, factorial, sine, cosine, tangent, reciprocal, base-10 and natural logarithms, eˣ, π, absolute value and Clear History.

Everything is computed on your own device as you press keys. Nothing is sent to a server and nothing is written to storage, so the display, the memory value and the history all start fresh on every page load.

Entering numbers and chaining operations

1. Type the first number. Only digits and one decimal point are accepted, up to twelve digits; extra keypresses are ignored.
2. Press an operator. It appears above the main display as a reminder of what is pending.
3. Type the second number and press = or Enter. The finished sum joins the history as, for example, 125 + 75 = 200.
4. A one-input function such as √ or sin applies as soon as you press it, with no = needed, and is logged as sqrt(144) = 12.

Pressing a second operator before = finishes the pending one first, so keys can be chained: 2 + 3 × leaves 5 on the display, and typing 4 then = gives 20. This is strict left-to-right evaluation with no operator precedence, which is how most pocket calculators behave but not how 2 + 3 × 4 is read in algebra, where the answer is 14. Press = between steps if the order matters.

Pressing an operator twice just changes which operator is pending, pressing = with nothing pending does nothing, and after a result the next digit starts a new number instead of extending the answer.

Button reference

Each one-input key works on whatever number is on the display at that moment. These behaviours were read from the calculation code, including the exact wording of the error messages.

Keyboard keys

• Digits 0 to 9.
• The decimal point.
• Plus and minus for add and subtract.
• Asterisk for multiply.
• Forward slash for divide.
• Percent sign to divide the display by 100.
• Enter or = to compute.
• Escape to clear.

The minus key is the subtraction operator, not a sign. There is no +/− key anywhere, so to get a negative number start from 0, subtract, and press =. The scientific functions have no keyboard equivalents.

Memory and history

The small indicator at the top left of the display shows the stored value and starts at M: 0. MC resets it to zero, MR copies it onto the display, M+ adds the displayed number to it and M− subtracts the displayed number from it.

One habit matters here: M+ and M− do not end the number you are typing. If you enter 50, press M+ and then type 25 without pressing C, the display becomes 5025 and the second M+ stores 5075. Press C after each M+ and the running total behaves as expected — 50, C, 25, M+ leaves 75 in memory.

The history panel keeps the last ten completed calculations, newest first, and drops the eleventh. Scientific functions are logged in function form, such as pow3(2) = 8. Clear History, on the Scientific layout, empties the list without touching the display or memory. Neither survives a reload.

Worked examples

Two square roots added

Press 144 √ to get 12, then + 25 √ =. The second root resolves to 5 before the addition runs, and the answer is 17. The history records all three steps: sqrt(144) = 12, sqrt(25) = 5 and 12 + 5 = 17.

A ratio of factorials

7 x! gives 5040 and 5 x! gives 120, so 7 x! ÷ 5 x! = returns 42. That is the number of ways to arrange two chosen items from seven in order, and it is far easier than cancelling the factorials by hand.

Edge case: sin 30 is not exactly 0.5

Enter 30 and press sin. The display shows 0.49999999999999994. The true value is one half; the shortfall is the smallest gap a 64-bit number can express, left over from converting degrees to radians. With 60 and cos the error runs the other way, 0.5000000000000001; tan 45 reads 0.9999999999999999 and sin 180 reads 1.2246467991473532e-16 instead of 0. Sine of 360 is the exception and shows a clean 0, because the input is reduced modulo 360 to exactly 0 first.

Edge case: a percentage mid-sum

Many people expect 200 + 10 % = to mean "add 10% of 200" and return 220. Here % converts the 10 into 0.1 on the spot, so the pending addition completes as 200.1. To add a tenth, multiply instead: 200 × 1.1 = returns 220.00000000000003, which is 220 with the usual binary rounding noise on the end.

Common mistakes

• Expecting algebraic precedence. 2 + 3 × 4 = gives 20 here, not 14, because each operator closes the one before it.
• Entering radians. Every angle is degrees, so π ÷ 6 then sin gives the sine of 0.52 degrees, which is about 0.0091, not 0.5.
• Forgetting C between memory additions, which appends digits to the number already shown.
• Trying to type a leading minus sign. Build negatives with 0 − n = instead.
• Reading floating-point noise as a bug. 0.1 + 0.2 = shows 0.30000000000000004 on every calculator that uses binary doubles, including this one.

Limits

Entry is capped at twelve digits, and arithmetic runs on standard 64-bit floating-point numbers, so values beyond roughly 10 to the 308th power are refused with Result is too large. Please use smaller values. rather than printed as infinity. Very large or very small results switch to exponent notation: 170 x! shows 7.257415615307994e+306.

There are no brackets, no expression line, no inverse or hyperbolic trigonometry, no radian mode, no arbitrary-base logarithm, no yˣ, no statistics, no complex numbers and no graphing. For exact fraction arithmetic use the fraction calculator; for one-step percentage and area work, the math calculators page.

Questions