Glide Path Descent Rate
Calculator
Results
- Rate of descent (ft/min)
- 689.944058
- Rule of thumb descent rate (ft/min)
- 650
- Descent gradient (ft per NM)
- 318.435719
Aviation and marine results
| Rate of descent (ft/min) | 689.944058 |
| Rule of thumb descent rate (ft/min) | 650 |
| Descent gradient (ft per NM) | 318.435719 |
formula-map diagram
- Rate of descent (ft/min)
- 689.944058
- Rule of thumb descent rate (ft/min)
- 650
- Descent gradient (ft per NM)
- 318.435719
Aviation and marine relationship
Formula
ROD = GS × tan(γ) × 6076.11548556556 ÷ 60= 689.94405840921
Note
This is a simplified model: it applies a standard navigation, performance or seamanship formula to the numbers you entered. True airspeed and density altitude use the ISA troposphere model for dry air and ignore humidity, compressibility and instrument or position error, so they are not a substitute for your aircraft's flight manual or an air data computer. Wind, climb, descent and fuel figures assume a steady wind and a constant speed and fuel flow for the whole leg; they ignore manoeuvring, holding, taxi and start-up fuel, terrain, turbulence and air traffic control routing. Takeoff distance scales an entered sea level figure by a rule-of-thumb percentage per 1000 ft of density altitude and is not a certified performance chart. Weight and balance results depend entirely on the arms and weights you enter and must be checked against the approved loading envelope. Hull speed is the classic 1.34 × √LWL displacement estimate, boat fuel burn is a horsepower-based approximation, anchor scope is a rule of thumb, and the rule of twelfths is a linear approximation of a sinusoidal tide that does not hold in all locations. Always use official charts, tide tables, the aircraft or vessel manuals and current weather, and treat these numbers as planning estimates only.
More in Aviation and marine
See all →Frequently asked questions
What is glide path descent rate and why is it important?+
It's the vertical speed needed to stay on a specified descent angle (commonly 3° for an ILS or visual approach) given your groundspeed. Flying the correct descent rate keeps you on the glide path all the way to the runway threshold instead of drifting high or low.
How is the descent rate calculated from groundspeed and descent angle?+
A common approximation is: descent rate (ft/min) = groundspeed (knots) × 5 × tan(descent angle), which for the standard 3° glide path simplifies closely to groundspeed × 5. For example, 120 knots groundspeed needs roughly a 600 ft/min descent to stay on a 3° path.
Why does the required descent rate change during an approach?+
As groundspeed changes — for example, slowing down as you approach the runway or due to changing headwind — the descent rate needed to maintain the same glide angle also changes. A constant descent rate only keeps you on a constant angle if your groundspeed stays constant too.
What's a common misconception about descent rate and descent angle?+
Pilots sometimes assume a fixed vertical speed, like 500 ft/min, always corresponds to a 3° glide path, but that's only true at one specific groundspeed. At higher groundspeeds you need a steeper (higher) rate of descent to maintain the same 3° angle.
How does wind affect the required descent rate?+
A headwind reduces groundspeed, so less vertical speed is needed to hold the same glide angle; a tailwind increases groundspeed and requires a higher rate of descent. This is why the same visual glide path can feel very different to fly on calm versus windy days.