How to use this calculator
- Enter climb rate. Use the corrected climb rate for the aircraft and condition.
- Enter ground speed. Use expected ground speed along the climb path.
- Enter distance. Set a horizontal distance to calculate altitude gained.
- Read gradient. Compare percent and ft/NM to the required climb performance.
How it works
The core relation is gradient = climb rate / ground speed. The calculator reports percent, feet per nautical mile, climb angle and altitude gain over the entered distance.
Use it with density altitude, crosswind component and weight and balance.
Worked example
Verified against the live calculator
At 700 ft/min and 85 kt ground speed, climb gradient is about 8.0 percent, or roughly 490 ft per nautical mile.
Frequently asked questions
How do you calculate climb gradient?
Climb gradient is rate of climb divided by ground speed, reported as percent and feet per nautical mile.
Why use ground speed instead of airspeed?
Obstacle clearance is about distance over the ground, so ground speed is the right input for gradient.
What is ft/NM?
Feet per nautical mile is the altitude gained for each nautical mile traveled over the ground.
Can this check obstacle departures?
It can screen the arithmetic, but approved procedure requirements and aircraft performance data control real planning.
Method & assumptions
- Assumes steady climb rate and ground speed over the checked segment.
- Does not replace aircraft performance charts, obstacle departure procedures, terrain analysis, wind correction or current density-altitude data.