Rate of Climb Calculator
Convert an altitude change and the time it took into a rate of climb in feet per minute, and the glide/climb gradient.
How it works
Rate of climb = altitude change ÷ time · Gradient = ROC ÷ (groundspeed × 6076 ÷ 60)
Rate of climb is just the altitude change divided by the time it took, expressed in feet per minute. Turning it into a gradient — feet gained per nautical mile forward, or a percentage — tells you whether you will clear terrain and obstacles, which depends on groundspeed as much as vertical speed. A high fpm at high groundspeed can still be a shallow gradient, so obstacle clearance always uses the gradient, not the vertical rate alone.
Worked example
Climbing from 3,000 to 4,000 ft in 2 minutes is 1,000 ÷ 2 = 500 fpm. At 90 kt groundspeed you cover 1.5 nm per minute, so the gradient is 500 ÷ 1.5 = 333 ft/nm, about 3.6%.
Sources: Rate of climb — Wikipedia
Frequently asked questions
What is the difference between rate and gradient of climb?
Rate of climb is vertical speed in feet per minute. Climb gradient is height gained per unit of horizontal distance (ft per nm or a percentage). Obstacle-clearance requirements are stated as gradients because they depend on how far you travel, not just how fast you rise.
Why does groundspeed affect the gradient?
For the same vertical rate, a faster groundspeed covers more horizontal distance while gaining that height, so the climb is shallower over the ground. That is why a strong tailwind can degrade your obstacle clearance even though the fpm is unchanged.
Can this show a descent?
Yes. Enter a negative altitude gained and the result becomes a negative rate — a rate of descent — with the summary describing the height lost over the time entered.
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This calculator is for educational purposes. Double-check important results before acting on them.