Required Descent Rate Calculator
To reach a crossing altitude at a fix or to arrive at the runway threshold on profile, you need the right descent rate. It depends only on how much altitude you must lose, the distance to the point, and your ground speed. This calculator gives the required vertical speed in feet per minute, the descent gradient in feet per nautical mile, and the equivalent glidepath angle. The geometry is exact and aircraft-independent.
Required descent rate formula
Time (min) = distance (nm) / ground speed (kt) * 60
Descent rate (ft/min) = altitude to lose / time
Gradient (ft/nm) = altitude to lose / distance
Angle = atan( gradient / 6076.12 ) in degrees
One nautical mile is 6,076.12 feet, used to convert the gradient to a glidepath angle.
Worked example
- Lose 9,000 ft over 30 nm at 250 knots ground speed.
- Time = 30 / 250 * 60 = 7.20 minutes.
- Descent rate = 9,000 / 7.20 = 1,250.00 ft/min.
- Gradient = 9,000 / 30 = 300.00 ft/nm, about a 2.83 degree path.
Descent rate: frequently asked questions
How do I calculate required descent rate?
Required descent rate in feet per minute = altitude to lose divided by the time available. Time available equals the distance to the target divided by your ground speed. A common shortcut is descent rate = ground speed in knots times the descent gradient in feet per nautical mile, divided by 60.
What is the 3 degree descent rule of thumb?
A 3 degree glidepath descends about 318 feet per nautical mile, often rounded to 300. A handy rule for feet per minute on a 3 degree path is ground speed in knots times 5. At 120 knots that is 600 feet per minute.
What is descent gradient?
Descent gradient is the altitude lost per unit of horizontal distance, often expressed in feet per nautical mile or as a percentage. Gradient in feet per nautical mile = altitude to lose / distance in nautical miles. A 318 feet per nautical mile gradient is a 3 degree path.
Does descent rate depend on aircraft type?
No. The required descent rate is pure geometry: it depends only on the altitude to lose, the distance, and the ground speed. Whether a given aircraft can achieve and stabilise on that rate is a separate performance question.
Official sources
- FAA: Instrument Procedures Handbook (descent planning).
- FAA: Aeronautical Information Manual (descent profiles).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.