Takeoff Runway Distance Calculator

Take-off distance vs. runway: TODR = ground roll + flare

Take-Off Distance Required (TODR) adds up two things: the ground roll until the aircraft rotates at V_R, and the airborne flare needed to clear a 35 ft obstacle. Several factors push it up. Weight W matters, so does pressure altitude and temperature (both of which raise density altitude), along with runway slope and any tailwind component. To put numbers on it, a Cessna 172 needs roughly 360 m at sea level in calm wind, while a Boeing 737-800 at MTOW wants about 1800 m. Runway 27R at Guarulhos (SBGR) runs 3700 m, so there is comfortable margin even for a B747. Under RBAC 121 the available runway has to exceed the TODR computed with an engine failure at V₁, and carriers end up trimming payload whenever the math doesn't close. As an example, take W = 2400 lb, PA = 2000 ft, OAT = 30 °C, which gives a TODR of about 540 m in a C172.

Applications

Pre-flight planning and W&B sheets. NOTAM-based go/no-go calls when works have shortened a runway. RBAC 121 mandatory take-off performance with the V₁/V_R/V₂ schedule. Hot-and-high analyses, corrections for a contaminated runway (water, snow, slush), and balanced-field length computations.

FAQ

What is balanced field length? It's the runway length where the accelerate-stop distance and the accelerate-go distance come out equal, which pins down the optimal V₁ for a given weight and the ambient conditions of the day.

Why is tailwind so penalizing? Every knot of tailwind raises the ground speed you need at rotation. That's why a lot of AFMs cap operational tailwind at 10 kt and call for hefty distance corrections.

Does runway slope matter? It does. An uphill slope brings in a gravity component that works against acceleration, and a 2% uphill on a 2000 m runway can tack 10-15% onto the TODR.