Calculator
Type an expression. You get the answer and the order it was reached in, because the useful part of 2 + 3 × 4 is not that it is 14 but that the multiplication happened first.
15 % 4
3
Try one
2 + 3 * 4 — multiplication before addition
(2 + 3) * 4 — brackets first
100 * (1 + 0.075/12)^12 — a year of monthly compounding
sqrt(16) + pow(2, 10) — functions
2/3 + 1/6 — fractions as division
15 % 4 — remainder
What it accepts
The four operations, powers with ^, remainder with %, brackets, and these functions: abs, ceil, floor, round, sqrt, cbrt, pow, exp, log, log10, log2, min, max, sign, hypot, mod, the trigonometric functions, gcd and lcm. The constants pi and e are available.
For anything with a formula behind it — a payment, a dose, a volume of concrete — the calculators give the derivation and the source as well as the number.