Glide Ratio and Range Calculator
Calculate glide ratio (L/D), maximum glide range from altitude, minimum descent rate, and best glide speed for any aircraft.
Essential for engine failure emergency planning.
Glide Ratio (L/D) The glide ratio (or lift-to-drag ratio, L/D) is the horizontal distance traveled per unit of altitude lost in a power-off glide. Glide ratio = L/D = Lift/Drag (dimensionless) In still air: Ground covered = Altitude × Glide ratio A glide ratio of 10:1 means the aircraft covers 10 units horizontally for every 1 unit of altitude lost.
Typical Glide Ratios Paper airplane: ~5:1 Light aircraft (Cessna 172): ~9:1 Jet airliner (Boeing 737): ~17:1 Business jet: ~15–20:1 Powered sailplane: ~40:1 High-performance glider: 50–70:1 Hang glider: ~12:1 | Paraglider: ~8–10:1
Best Glide Speed (Vbg) Best glide speed gives the maximum glide ratio (minimum drag, maximum L/D). Flying faster or slower than Vbg increases drag ratio and reduces range. In a headwind: increase speed above Vbg. In a tailwind: reduce speed toward Vstall + margin.
Minimum Sink Rate Minimum sink speed is slower than best glide speed — gives maximum time in the air. Used by glider pilots thermaling to stay in lift. Minimum sink = about 75–80% of best glide speed (roughly).
Wind Effect on Glide Headwind component reduces effective glide range. Effective ground glide ratio = (V_tas − V_headwind) / sink_rate For engine failure: adjust heading to minimize headwind, maximize groundspeed.
Engine Failure Emergency After engine failure, pilot should immediately establish best glide speed. Identify the highest reachable airport within glide range. Call mayday: 121.5 MHz (Emergency frequency). Glide range (no wind) = Altitude AGL × Glide ratio