Glide Distance Calculator (How Far Can I Glide After an Engine Failure?)
How far an aircraft, glider or paraglider can glide from a given height, from its glide ratio, with the effect of headwind or tailwind and the time in the air.
Results
The dashed line marks the value you entered.
What this tool does
The glide ratio is the distance covered for each unit of height lost: at 9:1, every 1,000 ft of height buys about 9,000 ft (1.5 NM) in still air; modern gliders reach 40:1 and more. A headwind does not change how long you stay up, but it cuts the distance by the fraction (V − headwind) ÷ V, so a 10 kt headwind at 65 kt costs about 15 %. Use the speed for best glide from the flight manual, and treat the answer as a ceiling: turns, a windmilling propeller, sink in the air and the need to pick a field and a pattern reduce it.
Formula
still-air distance = height × glide ratio · over the ground × (V − headwind) ÷ V · sink rate = V ÷ glide ratio
Variables
| Symbol | Meaning | Unit |
|---|---|---|
h | Height above the ground | ft |
ld | Glide ratio (distance forward per unit of height lost) | — |
va | Airspeed you glide at | kt |
hw | Headwind (negative for tailwind) | kt |
GD | Distance you can glide over the ground | NM |
GK | The same in kilometres | km |
GN | Distance in still air | NM |
GT | Time in the air | min |
SR | Rate of sink | ft/min |
Worked example
- Height above the ground5000 ft
- Glide ratio (distance forward per unit of height lost)9
- Airspeed you glide at65 kt
- Headwind (negative for tailwind)10 kt
- Distance you can glide over the ground6.3 NM
- The same in kilometres11.6 km
- Distance in still air7.4 NM
- Time in the air6.8 min
- Rate of sink731 ft/min
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.