Order of operations
Type an expression and the result appears as you type. The calculator follows standard precedence: multiplication and division are done before addition and subtraction, and anything in parentheses is worked out first. So 2 + 3 × 4 is Please check your expression: Unexpected character: "_", while (2 + 3) × 4 is Please check your expression: Unexpected character: "_". Operations of equal precedence are evaluated from left to right.
How the % key works here
Percentages are a common source of confusion because calculators handle them differently. In this calculator, a percentage added to or subtracted from a number is taken as a percentage of that number, which is usually what people mean when adjusting a price: 50 + 10% is 55 and 200 − 10% is 180. Anywhere else, X% simply means X divided by 100, so 200 × 10% is 20 and 10% on its own is 0.1.
Memory
The memory keys keep a running total while you work: M+ adds the current result to memory, M− subtracts it, MR puts the stored value back into the expression, and MC clears it. The stored value is shown next to the keys and lasts until you leave the page.
Errors
Dividing by zero is reported as an error instead of showing "Infinity", and an incomplete expression such as an unclosed parenthesis is flagged so you can fix it. Results are shown to up to 10 significant digits.