Aviation Rate of Climb (ROC) Calculator
Calculate the required Rate of Climb in feet per minute (FPM) based on your ground speed and the required climb gradient.
Required Rate of Climb:
0 FPM
Understanding Rate of Climb (ROC)
Rate of Climb (ROC) is the vertical speed of an aircraft, typically measured in feet per minute (fpm). In aviation, accurately calculating ROC is critical for safety, specifically for ensuring obstacle clearance during departure and complying with Air Traffic Control (ATC) instructions or Standard Instrument Departure (SID) requirements.
The Rate of Climb Formula
While climb gradients on charts are often provided in feet per nautical mile (ft/nm), aircraft instruments display vertical speed in feet per minute (fpm). To bridge this gap, pilots use the following formula:
ROC (fpm) = [Ground Speed (kts) / 60] × Climb Gradient (ft/nm)
Because ground speed is horizontal distance per hour, dividing it by 60 gives the distance traveled per minute. Multiplying that by the gradient (the vertical rise required per unit of horizontal distance) provides the necessary vertical speed.
Why Ground Speed Matters
It is important to remember that climb gradients are relative to the ground. Therefore, you must use Ground Speed, not Indicated Airspeed, for this calculation. A strong headwind will decrease your ground speed, meaning you need a lower ROC to maintain the same gradient. Conversely, a tailwind increases ground speed, requiring a much higher ROC to clear the same obstacles.
Practical Example:
Imagine you are flying a departure procedure that requires a climb gradient of 350 ft/nm. Your aircraft has a ground speed of 140 knots.
- Divide GS by 60: 140 / 60 = 2.33
- Multiply by Gradient: 2.33 × 350 = 815.5
- Required ROC: 816 feet per minute.
Factors Affecting Climb Performance
- Density Altitude: High temperatures and high elevations reduce engine performance and wing lift, decreasing the maximum achievable ROC.
- Aircraft Weight: A heavier aircraft requires more lift and thrust to climb, resulting in a lower maximum rate of climb compared to a lighter load.
- Flap Settings: While flaps increase lift, they also increase drag, which usually reduces the overall rate of climb.