Independent Variables:
Speed (V), Angle (A) and Height of Release (H)

Time of flight can be found by solving the equation of vertical motion using the quadratic formula:

Note that the plus/minus sign gives two solutions for the time when Y = 0. These correspond to the time at the end of flight (negative sign) and the time at the beginning of flight (if the projectile had started from ground level). Also recognize that if H = 0, then the time of flight reduces to

t = (-2 * vertical velocity)/g

which is expected for takeoff from ground level.