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Glide Ratio Calculator

Reviewed by the CalculatorHub team, edited by James Graham. Standard aerodynamic glide ratio (L/D) formula. Last verified 14 June 2026.

Glide ratio is the horizontal distance traveled per unit of altitude lost in unpowered flight. It is numerically equal to the lift-to-drag (L/D) ratio at best glide speed. Knowing your aircraft's glide ratio and your altitude above terrain allows you to determine your glide distance in an engine failure emergency. This calculator works in two modes: given altitude and glide ratio, it computes maximum glide distance; given horizontal distance and altitude, it computes the required glide ratio to reach that point.

Your current altitude minus terrain/pattern altitude (AGL)
From POH at best glide speed (e.g. 9 means 9:1)
54,000.00 ft
8.91 nm
10.23 mi

Glide ratio and glide distance formulas

Glide Distance (ft) = Altitude (ft) x Glide Ratio
Glide Distance (nm) = Glide Distance (ft) / 6,076.12
Required Glide Ratio = Horizontal Distance / Altitude

Glide ratio equals the lift-to-drag ratio (L/D) at best glide speed. For steady unpowered glide in still air, the glide angle equals arctan(1 / glide ratio). The horizontal distance covered is the initial altitude multiplied by the glide ratio. One nautical mile = 6,076.12 feet; one statute mile = 5,280 feet.

Emergency planning: using glide ratio

  • In an engine failure, immediately pitch to best glide speed. Memorize this speed for your aircraft.
  • Calculate usable height: subtract 1,000 ft for traffic pattern maneuvering from your AGL altitude.
  • Multiply usable height by your glide ratio to get maximum glide distance in feet; divide by 6,076 for nautical miles.
  • Identify suitable landing areas within the glide circle on your chart or EFB.
  • Account for headwind: with a 10-knot headwind at 90 knots TAS, glide ratio over ground is reduced by about 10%.

Glide ratio calculator: frequently asked questions

What is glide ratio?

Glide ratio (also called lift-to-drag ratio, or L/D ratio) is the horizontal distance an aircraft travels for every unit of altitude lost in unpowered flight. A glide ratio of 10:1 means the aircraft travels 10 feet forward for every 1 foot of altitude lost. Glide ratio is a fundamental measure of aerodynamic efficiency.

What is the best glide speed?

Best glide speed is the airspeed that gives the maximum glide ratio, meaning the maximum horizontal distance per unit of altitude lost. It is published in the POH and is usually expressed in knots indicated airspeed (KIAS). Flying above or below best glide speed reduces glide ratio and shortens the glide distance. Best glide speed varies slightly with aircraft weight.

How do I calculate glide distance?

Glide distance = altitude above terrain x glide ratio. If your aircraft has a 9:1 glide ratio and you are at 6,000 ft above terrain, your maximum glide distance is 6,000 x 9 = 54,000 ft, which is approximately 8.9 nautical miles. Always subtract traffic pattern altitude (about 1,000 ft AGL) from your available altitude to get usable glide height.

Does headwind or tailwind affect glide ratio?

Wind affects your glide ratio over the ground but not through the air. With a headwind, your ground glide ratio is reduced (you cover less distance over the ground). With a tailwind, ground glide ratio improves. For emergency planning, use the worst-case wind assumption. The aerodynamic glide ratio through the air is unchanged by wind.

What is a typical glide ratio for light aircraft?

Light single-engine piston aircraft typically have glide ratios of 8:1 to 12:1. High-performance sailplanes achieve ratios of 40:1 to 70:1. The Space Shuttle had a glide ratio of approximately 4.5:1 when unpowered. Commercial airliners typically glide at 17:1 to 20:1. A Boeing 767 with engines off can glide approximately 100 miles from 40,000 ft.

Official sources

Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.