10 free math and science calculators — scientific, fractions, percentages, triangle solver, random number generator, quadratic formula, statistics, grades, unit conversion & number systems.
The difference between a calculator and a solver is whether it shows the reasoning. The tools here lean towards solvers: the quadratic tool reports the discriminant, not just the roots, because the sign of b² − 4ac tells you what kind of answer to expect before you compute it. For 2x² + 5x − 3 the discriminant is 5² − 4 × 2 × (−3) = 49, a perfect square, which guarantees two clean rational roots — and indeed x = 0.5 and x = −3. A negative discriminant would have meant no real roots at all.
Fractions are a genuine representation problem rather than a convenience. A third cannot be written exactly in decimal, so any calculator that converts to decimal first accumulates error, and adding thirds repeatedly will eventually fail to give a whole number. A fraction calculator keeps numerator and denominator as integers throughout and reduces only at the end, which is the only way to stay exact.
Statistics carries the subtlest trap on this page: dividing by n or by n − 1. For the set 2, 4, 4, 4, 5, 5, 7, 9 the mean is 5, and the standard deviation is 2.0000 if those eight values are your entire population but 2.1381 if they are a sample drawn from something larger. The second is always the bigger number, because a sample understates the spread of the population it came from, and the n − 1 correction compensates for exactly that bias.
Number-base tools convert by repeated division, keeping remainders in reverse order — which is why 156 becomes 10011100 in binary and 9C in hexadecimal, and why hex is the compact way to read binary: each hex digit stands for precisely four bits.