What is the standard descent gradient for an ILS approach?

Most precision approaches use a 3-degree glideslope, which corresponds to approximately 318 feet per nautical mile (5.24%). At a typical approach speed of 120 knots ground speed, 3 degrees translates to roughly 636 FPM. The exact FPM depends on your ground speed — this calculator adjusts automatically.

What is a typical rule of thumb for descent rate?

A common pilot rule of thumb is: multiply your ground speed (in knots) by 5 to get the approximate FPM needed for a 3-degree descent. For example, 120 knots × 5 = 600 FPM. This calculator uses the exact formula rather than the approximation, giving you the precise value for any combination of altitude loss, distance, and speed.

How do I find the top of descent (TOD) point?

The TOD is the point where you should begin your descent. A common rule is: altitude to lose (in thousands of feet) × 3 = distance to start descending in nautical miles. For example, needing to lose 10,000 ft means starting about 30 nm out. Use this calculator to verify the required FPM matches your aircraft capability once you have your TOD point.

What descent rates are considered normal vs. excessive?

For most commercial and GA operations, a descent rate of 500–1,500 FPM is considered comfortable. Rates above 2,000 FPM may be acceptable in jets during cruise descent but can be uncomfortable for passengers. For visual approaches and non-precision approaches, anything below 1,000 FPM at the threshold is generally stable. Always follow your airline or aircraft operator's stabilized approach criteria.

Why does ground speed matter for descent rate?

Descent rate (FPM) is a function of both the vertical distance to cover and the time available. At a higher ground speed you cover horizontal distance faster, leaving less time to lose altitude — so you need a steeper FPM. At a lower ground speed you have more time for the same descent, reducing the required FPM. This is why you must always calculate FPM based on your actual ground speed, not airspeed.

What is descent gradient and why is it useful?

Descent gradient (expressed as a percentage or in feet per nautical mile) describes the vertical profile independent of airspeed. Standard IFR approach gradients are published in procedure charts (e.g., 3.00° or 318 ft/nm). Comparing your required gradient against published values helps quickly identify if an approach profile is within normal limits regardless of the specific ground speed.

Descent Rate Calculator

Name: Descent Rate Calculator
Availability: InStock
Author: Nham Vu

Enter current altitude, target altitude, distance to go, and ground speed to find the required descent rate in feet per minute.

Descent Parameters

Current Altitude (ft)

Your present altitude or top of descent altitude.

Target Altitude (ft)

Altitude to reach at the fix or waypoint.

Distance to Go (nm)

Horizontal distance in nautical miles to the target fix.

Ground Speed (kt)

Actual ground speed, not indicated airspeed.

3-Degree Glidepath Reference

Ground Speed	Required FPM

Based on a 3.00-degree descent angle (318 ft/nm).

Enter your descent parameters and click Calculate.

Required descent rate and angle appear here.

Summary