How do you calculate glide ratio?

Divide the horizontal distance traveled by the height lost, in the same units. Losing 1,000 ft while covering 9,000 ft is 9:1. From instruments, divide horizontal speed by sink rate: 38 km/h (10.56 m/s) with a 1.1 m/s sink is about 9.5:1. In still air the glide ratio equals the lift-to-drag ratio (L/D).

How far can I glide from my altitude?

Still-air glide distance = height above ground × glide ratio. At 9:1 from 5,000 ft AGL that is 45,000 ft, or 7.4 NM (8.5 statute miles, 13.7 km). Pilots often use the shortcut "nautical miles per 1,000 ft = glide ratio ÷ 6".

How does wind change glide distance?

Wind moves the air mass, so the ratio through the air is unchanged but the distance over the ground is not. Ground distance = height × L/D × groundspeed ÷ airspeed. A 9:1 aircraft at 65 kt into a 15 kt headwind has an effective ratio of about 6.9:1, so 5,000 ft gives 5.7 NM instead of 7.4 NM. Into a headwind, flying a little faster than best-glide speed recovers some distance.

What is the glide angle for a given glide ratio?

Glide angle γ = arctan(1 ÷ glide ratio). A 9:1 glide is a 6.3° descent (an 11.1% gradient, about 675 ft per nautical mile); 34:1 is 1.7°.

How is sink rate calculated?

Sink rate = true airspeed × sin(glide angle). At 65 kt and 9:1 that is about 727 ft/min (3.69 m/s). The common shortcut airspeed ÷ glide ratio gives 731 ft/min; it is within 1% for ratios above 7:1.

Does weight change the glide ratio?

No. A heavier or lighter aircraft has the same best L/D, so the same glide distance from a given height, but the best-glide speed changes with the square root of weight: V = V(max weight) × √(W ÷ W max). At 80% of max weight, 65 kt becomes about 58 kt.

What is a typical glide ratio?

Light single-engine airplanes are about 8:1 to 11:1, paragliders 8:1 to 11:1, hang gliders 10:1 to 17:1, airliners roughly 15:1 to 20:1, training sailplanes such as the ASK 21 about 34:1, and open-class sailplanes 55:1 to 70:1. Always use the figure in your POH or flight manual.

Glide Ratio Calculator

Glide ratio = horizontal distance ÷ height lost. Enter distance and height, airspeed and sink rate, or a published L/D to get the ratio, glide angle, sink rate, time aloft and how far you can glide from your height with a headwind or tailwind.

Glide Inputs

I know the glide as

Lift-to-drag ratio (L/D)

9 means 9:1. Use the best-glide figure from your POH or flight manual.

True airspeed (optional here)

Needed for sink rate, time aloft and wind. The unit also applies to wind.

Height above ground (optional)

Wind component

Direction

Distance to landing spot (optional)

Examples (check your own manual)

Glide Ratio

— : 1

Glide angle

—

Descent gradient

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Sink Rate & Time Aloft

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ft / min

—

m / s

—

min aloft

Glide Distance from Height

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nautical miles

—

statute miles

—

kilometers

Still air.

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Best-Glide Speed at a Lighter Weight

V = V_published × √(weight ÷ max weight). The glide ratio stays the same; only the speed that achieves it changes.

Published speed

At weight

Actual weight

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Typical Best Glide Ratios

Still-air distance per 1,000 ft (305 m) of height. Approximate; your flight manual governs.

Aircraft	Glide ratio	Angle	NM per 1,000 ft
Space Shuttle orbiter (subsonic)	4.5:1	12.5°	0.7
Light single (Cessna 172, PA-28)	8–11:1	5.2–7.1°	1.3–1.8
Paraglider (EN-A to EN-D)	8–11:1	5.2–7.1°	1.3–1.8
Hang glider	10–17:1	3.4–5.7°	1.6–2.8
Jet airliner, clean	15–20:1	2.9–3.8°	2.5–3.3
Training sailplane (ASK 21)	34:1	1.7°	5.6
15 m / Standard class sailplane	40–48:1	1.2–1.4°	6.6–7.9
Open class sailplane	55–70:1	0.8–1.0°	9.1–11.5

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Summary

Glide ratio is the horizontal distance an unpowered aircraft covers for each unit of height it loses. In still air it equals the lift-to-drag ratio (L/D), because the glide path angle γ satisfies tan γ = D/L = 1/(L/D). This calculator finds the ratio three ways (distance ÷ height lost, horizontal speed ÷ sink rate, or a published L/D), then derives the glide angle, descent gradient, sink rate (airspeed × sin γ), time aloft and glide distance from a given height. Wind changes the distance over the ground but not the ratio through the air: ground distance = height × L/D × groundspeed ÷ horizontal airspeed. Use true airspeed for sink rate and wind math, and treat results as planning estimates, not a substitute for the POH or flight manual.

How it works

Pick how you know the glide: a published L/D, a measured distance and height lost, or airspeed and sink rate (the way paraglider and sailplane polars are quoted).
Enter airspeed to get sink rate, time aloft and wind correction. Height above ground gives the still-air glide distance (height × glide ratio).
Add a headwind or tailwind component: groundspeed = horizontal airspeed ∓ wind, and the effective ratio over the ground = glide ratio × groundspeed ÷ horizontal airspeed.
Enter the distance to a landing spot to see the ratio required (distance ÷ height) and the height you would arrive with.
For a lighter aircraft, the best-glide speed panel scales the published speed by √(weight ÷ max weight); the glide ratio itself does not change with weight.

Use cases

Engine-out planning: how far a Cessna 172 (about 9:1) glides from 5,000 ft AGL (7.4 NM in still air, 5.7 NM into a 15 kt headwind).
Working out a measured glide ratio from a flight log: 12 km flown while losing 1,000 m is 12:1.
Turning a paraglider polar (38 km/h trim, 1.1 m/s sink) into a glide ratio (about 9.5:1).
Checking whether a field 6 NM away is reachable from 4,000 ft with the current wind.
Finding the best-glide speed at a lighter weight, and the glide angle and descent gradient for an approach.
Comparing gliders, hang gliders, paragliders and powered aircraft by glide performance.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu