Descent Rate Calculator

About this calculator

An aircraft's descent rate — measured in feet per minute — is the vertical speed a pilot must fly to stay on a chosen glidepath angle at a given groundspeed. The relationship is straightforward trigonometry: descent rate ≈ groundspeed × tan(glidepath angle), commonly simplified with rules of thumb like the “3-in-1” rule pilots use for a standard 3-degree approach. This calculator computes the exact descent rate and altitude lost per nautical mile from your groundspeed and glidepath angle.

This figure is essential during instrument and visual approach planning: pilots cross-check their vertical speed indicator against the computed target rate to confirm they're tracking the glidepath correctly, whether flying an ILS, a visual approach, or a non-precision approach with a defined descent angle. Flight instructors also use the calculation to teach stabilized-approach technique, since flying too fast or too slow a descent rate relative to the required glidepath is a common cause of unstable approaches.