Scientific calculator
Trigonometry, logarithms, powers and roots — with the expression visible and editable, the degree conversion written down rather than hidden in a mode flag, and every reduction shown in the order precedence applies it.
By Alex Seote, Built and maintains Rule Calculator
Precedence and functions checked against the evaluator's tests · How we check
Equals
14
The order it worked in
- 1. 3 * 4 = 12
- 2. 2 + 3 * 4 = 14
Each line reduces one operation, in the order the rules of precedence apply them.
The mode flag is the bug
Ask a hundred people why their trigonometry answer is wrong and the answer is the same: the calculator was in radians and they meant degrees, or the reverse. The flag is a three-letter abbreviation in a corner of a display, it persists between sessions, and nothing in the answer reveals which one produced it.
Writing sin(pi / 180 * 30) instead of flipping a switch costs a few characters and removes the failure mode entirely: the expression carries its own units, and anyone reading it afterwards — including you, tomorrow — can see what was meant.
Questions people actually ask
- Why does my calculator give a different answer for sin(30)?
- Because it is in the other mode. In degrees sin(30) is exactly 0.5; in radians it is about −0.988. Every pocket calculator carries that flag in a corner of the display, and reading it wrong is the most common wrong answer in trigonometry. Here the degree conversion is written into the expression itself — sin(pi / 180 * 30) — so what the machine is doing is visible in what you typed.
- What order does it apply operations in?
- Brackets, then powers, then multiplication and division left to right, then addition and subtraction left to right. So 2 + 3 × 4 is 14 rather than 20. The working underneath the answer reduces one operation per line in that order, which turns a disagreement with your own arithmetic into something you can locate rather than argue with.
- What is the difference between ln and log?
- The base. ln is the natural logarithm, base e, which is the one that appears in growth, decay and compound interest. log on this page and on most scientific calculators written for schools means base ten. Both keys are here and both are labelled, because "log" alone is ambiguous enough that the two conventions have caused real errors in published work.
- Can I edit an expression instead of starting over?
- Yes — the box is a text field, so a mistyped digit is a click away from being fixed rather than a reason to clear everything. Kept results go into a list you can tap to bring back. A pocket calculator forgets what you typed the instant it answers, which is a limitation of a seven-segment display rather than a design decision worth copying.
- Is anything sent to a server?
- The arithmetic happens in your browser. The evaluator is the same one the rest of this site uses: expressions are parsed and checked against a whitelist of functions before they run, so nothing beyond arithmetic can be expressed — no property access, no assignment and no loops.