Climb gradient calculator
Convert between feet per minute, feet per nautical mile, and percentage gradient.
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.
Live: where climb performance is worst right now
The highest density altitudes currently being reported. Climb rate degrades with density altitude, so these are the fields where a published departure gradient is hardest to make.
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For planning and study, not for operational use. Aircraft performance comes from your POH, not from a generic formula.