Climb Gradient Calculator
Climb gradient, expressed in feet per nautical mile (ft/nm) or as a percentage, is the key performance metric for instrument departures, obstacle clearance, and SID compliance. Unlike rate of climb (which is purely vertical), gradient relates vertical performance to horizontal distance covered. A slow ground speed with a high rate of climb gives a steep gradient; a fast ground speed requires an even higher rate of climb to achieve the same gradient. This calculator takes rate of climb and ground speed as inputs and computes the gradient in ft/nm and as a percentage. You can also find the rate of climb required to meet a given gradient at a known ground speed.
Climb gradient formula
Gradient (ft/nm) = ROC (ft/min) x 60 / GS (knots)
Gradient (%) = Gradient (ft/nm) / 6,076.1 x 100
ROC required (ft/min) = Required Gradient (ft/nm) x GS / 60
One nautical mile = 6,076.1 feet. Converting ft/nm to a percentage divides by 6,076.1 and multiplies by 100. The standard FAA obstacle clearance gradient of 200 ft/nm equals approximately 3.29%. Published SID climb gradients use ft/nm. Note: 6,076 ft/nm x percent/100 gives the equivalent ft/nm.
SID climb gradient compliance
- If a SID requires 200 ft/nm and your ground speed is 120 knots, you need ROC = 200 x 120 / 60 = 400 ft/min minimum.
- If a SID specifies 340 ft/nm (equivalent to a 3-degree climb angle) at 90 knots GS, you need 510 ft/min ROC.
- Always verify ROC using your aircraft's performance charts at the actual weight, temperature, and density altitude.
- Climb gradient requirements cannot be met by a simple ROC check. The ground speed at the time of departure is critical.
Climb gradient calculator: frequently asked questions
What is a climb gradient?
Climb gradient is the vertical distance gained per unit of horizontal distance traveled, expressed as feet per nautical mile or as a percentage. It is distinct from rate of climb, which is vertical feet per minute. Gradient depends on both climb rate and ground speed.
Why is climb gradient important for IFR departures?
FAA Standard Instrument Departures (SIDs) and diverse vector areas specify minimum climb gradients (e.g., 200 ft/nm) to ensure obstacle and terrain clearance. If the aircraft cannot meet the published gradient, the crew must use alternate departure procedures or restrict weight.
How is climb gradient calculated from ROC and ground speed?
Climb Gradient (ft/nm) = Rate of Climb (ft/min) / Ground Speed (nm/min). Since ground speed in knots equals nm per hour, divide by 60 to get nm per minute. So: ft/nm = (ROC in ft/min) / (GS in knots / 60) = (ROC x 60) / GS.
What is the relationship between climb gradient and climb angle?
The climb angle in degrees = arctan(gradient in ft/nm / 6,076.1). For a 200 ft/nm gradient, the angle is arctan(200/6076) = 1.89 degrees. A standard 3-degree glidepath corresponds to approximately 318 ft/nm descent gradient.
Does wind affect climb gradient?
Yes. A headwind reduces ground speed, which increases the climb gradient for a given rate of climb. This is beneficial for obstacle clearance. A tailwind increases ground speed and reduces gradient. Ground speed (not TAS) is used to calculate the over-ground gradient.
Official sources
- FAA Instrument Procedures Handbook (FAA-H-8083-16B), Chapter 3 Departures: faa.gov.
- FAA AIM Section 5-2 (Departure Procedures): faa.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.