This free online quadratic formula calculator solves any equation of the form ax² + bx + c = 0 for x. Enter the coefficients a, b, and c to instantly get the real or complex roots, worked out with the quadratic formula.
How to Use the Quadratic Formula Calculator
Enter the coefficient of x² in field "a".
Enter the coefficient of x in field "b".
Enter the constant term in field "c".
Click "Calculate" to see the roots (solutions) of the equation.
Frequently Asked Questions
It applies the quadratic formula x = (-b ± √(b² - 4ac)) / 2a, first computing the discriminant b² - 4ac to determine what kind of roots exist.
A negative discriminant means there are no real solutions, so the calculator returns two complex roots in the form "real part ± imaginary part i", for example x = 1 ± 2i, and labels the result "Two complex roots".
If a is 0, the x² term disappears and the equation is no longer quadratic, so the calculator shows "a cannot be zero — not a quadratic equation" instead of a result.
Yes, it's completely free with no sign-up required.