About the Time of Flight Calculator – Projectile Motion
Time of flight is the total duration a projectile spends in the air, from the instant it launches until it reaches the landing height. For a launch and landing at the same height, the classic formula is T = 2v₀sin(θ)/g. This calculator uses the more general form that also accounts for a launch height above the landing point, so it works for problems like a ball kicked from a rooftop or a projectile fired from an elevated platform, not just launches starting at ground level.
Deriving the time-of-flight formula
Projectile motion splits into two independent components: horizontal motion at constant velocity vₓ = v₀cos(θ), and vertical motion under constant gravitational acceleration g, with initial vertical velocity vy₀ = v₀sin(θ). Starting from launch height h₀, the vertical position at time t is y(t) = h₀ + v₀sin(θ)t − ½gt². Setting y(t) = 0 and solving the resulting quadratic for t gives the general time of flight: T = [v₀sin(θ) + √((v₀sin(θ))² + 2gh₀)] / g. When h₀ = 0, the square root simplifies to v₀sin(θ) and the expression reduces to the familiar T = 2v₀sin(θ)/g. The same vertical component gives the maximum height H = h₀ + (v₀sin(θ))²/(2g), reached at t = v₀sin(θ)/g. Combined with the constant horizontal speed, this also gives the horizontal range R = vₓ × T and, from energy conservation, the impact speed at landing.
Practical notes and common mistakes
- Angle convention: θ is measured from the horizontal, not the vertical. A 90° angle means straight up (zero horizontal range); a 0° angle means a flat, horizontal launch.
- This model ignores air resistance. Drag reduces both range and time of flight, sometimes substantially for lightweight or high-speed projectiles such as golf balls, arrows, or bullets. Treat the result as an ideal upper bound.
- Match gravity to your planet and unit system. Earth's standard gravity is 9.81 m/s² (32.2 ft/s²); the Moon is about 1.62 m/s² and Mars about 3.72 m/s². Mixing unit systems between velocity, height, and gravity is the most common source of wrong answers.
- Launch height extends flight time, not the range formula directly — range is still vₓ × T, but T itself grows because gravity has farther to pull the projectile down before it reaches the landing plane.