Estimate peak altitude, velocity and time to apogee (with air drag) from your airframe and motor, plus the parachute descent rate.
Peak altitude
429 m
1,406 ft
Velocity at burnout
119.1 m/s
429 km/h
Maximum velocity
119.1 m/s
429 km/h
Time to apogee
8.8 s
Burnout at 1.5 s
Altitude profile (time vs. altitude)
PoweredCoastAltitude (m)
For education and simulation only — figures are estimates. Real launches must use certified motors and follow NAR or your country's safety code, launch permissions, and range rules.
Source: estimates based on standard rocket flight dynamics (numerical integration of the equations of motion) and typical published model-rocket motor data.
What is the Model Rocket Flight Calculator?
This calculator estimates how high a model rocket will fly (its apogee, or peak altitude), how fast it is going at motor burnout, its top speed in flight, and how long it takes to reach the peak — all with air drag included. It puts the three forces acting on the rocket (gravity, thrust and drag) into the equations of motion and integrates them numerically over small time steps, producing a realistic flight curve rather than a single simplistic formula. A separate descent mode computes the parachute's terminal (descent) speed and tells you whether it lands at a safe rate.
How to use
1. In Flight mode, enter the airframe mass (g), body diameter (mm) and drag coefficient (Cd).
2. Enter the motor's average thrust (N) and burn time (s), or tap a motor preset (A8, B6, C6, etc.) to fill them in.
3. See the peak altitude, burnout velocity, maximum velocity and time to apogee, plus an altitude-versus-time profile.
4. Switch to Descent mode and enter mass, parachute diameter (mm) and parachute Cd to get the descent rate and a safe-zone verdict.
How it is calculated
The rocket feels an upward thrust T, a downward weight m·g, and a drag force D opposing its motion. Drag is D = ½·ρ·Cd·A·v², where ρ is air density, Cd the drag coefficient, A the rocket's frontal area and v its speed. During the burn (0 to burn time) thrust acts; after burnout thrust is zero and the rocket coasts upward under gravity and drag alone. The net acceleration a = (T − m·g − D)/m is integrated over tiny time steps to update velocity and altitude; the point where velocity reaches zero is the apogee (peak altitude). For parachute descent the terminal velocity v = √(2·m·g / (ρ·Cd·A)) gives the steady descent speed where weight and drag balance.
How to read the results
Peak altitude (apogee) helps you judge safety margins and the recovery area. Burnout velocity is how fast the rocket is moving as it switches from powered flight to coasting, indicating whether it left the launch rod fast enough for stable flight. The altitude profile is colour-split into the powered phase (solid) and the coast phase (dashed) so you can see the climb to apogee. In descent mode, a descent rate inside the 3–6 m/s safe zone is a good balance: not so slow that it drifts away in the wind, not so fast that landing damages the rocket.
FAQ
What determines the peak altitude? ▾
It comes from the balance of the motor's total impulse (the punch from thrust applied over time) against the rocket's mass and air drag. More impulse, less mass and lower drag all mean a higher flight. After burnout, gravity and drag slow the rocket; the point where its speed hits zero is the apogee.
How much does air drag matter? ▾
A lot. Drag rises with the square of speed, so it bites hardest on fast rockets. Simple calculations that ignore drag tend to badly overestimate altitude. This tool includes drag in the equations of motion and integrates numerically, giving more realistic heights — try changing the Cd or body diameter to feel the effect.
What is the difference between thrust and impulse (N·s)? ▾
Thrust (N) is the force the motor produces at an instant; impulse (N·s) is that thrust summed over the burn time — the total push. Total impulse equals the momentum delivered to the rocket, and a motor's class (A, B, C…) is defined by its total-impulse range. For the same impulse, a high-thrust short-burn motor accelerates sharply, while a low-thrust long-burn motor pushes gently for longer.
What is a safe descent rate? ▾
Around 3–6 m/s is the usual guideline. Too slow and the rocket drifts off in the wind and is hard to recover; too fast and it can be damaged or dangerous on landing. Use a larger parachute or a higher-Cd shape to slow the descent.
What are motor classes (A, B, C)? ▾
They classify motors by total impulse (N·s). Each letter roughly doubles the upper impulse limit of the one before (A = 1.26–2.5 N·s, B = 2.5–5, C = 5–10, …). The number after the letter is the average thrust (N). For example, C6 is a C-class motor with 6 N average thrust.