Climb Gradient Calculator

How it works

ft/NM = rate of climb × 60 ÷ groundspeed. Percentage gradient = ft/NM ÷ 6,076 × 100.

Why departure procedures use ft/NM

An obstacle sits at a fixed distance from the runway, not a fixed time, so the requirement has to be expressed per unit of distance. The standard climb gradient is 200 ft/NM; anything higher is published on the chart, and it is a requirement rather than a suggestion.

The trap

A gradient in ft/NM gets harder to meet as groundspeed increases — you are covering the ground faster, so you have less time to gain the height. A tailwind on departure is the case people miss: the same 600 fpm that comfortably made 200 ft/NM at 90 kt falls short at 120 kt.