How do you convert a climb gradient to a rate of climb?

Rate of climb (fpm) = gradient (ft/NM) × groundspeed (kt) ÷ 60. A 200 ft/NM gradient at 90 knots groundspeed needs 200 × 90 ÷ 60 = 300 feet per minute. The reverse works too: gradient = fpm × 60 ÷ groundspeed.

Why does the climb gradient use groundspeed instead of airspeed?

A gradient is height gained per distance over the ground, so the speed that matters is the speed over the ground. A headwind slows your groundspeed and makes any published gradient easier to meet at the same rate of climb; a tailwind on departure does the opposite. High density altitude hurts twice: the engine gives you less rate of climb while your true airspeed, and usually groundspeed, goes up.

Where does the standard 200 ft/NM climb gradient come from?

Instrument departure procedure design (TERPS) assumes at least 200 feet per nautical mile after crossing the departure end of the runway at 35 feet, unless the procedure publishes a higher gradient or a climb-over-airport option. If an obstacle departure procedure or SID lists a number bigger than 200, that number is the one your airplane has to beat, to the altitude the procedure states.

What if my aircraft can't meet a published climb gradient?

Don't fly the procedure on hope. Options include a different runway or departure, a visual climb over the airport where one is published, waiting for cooler temperatures or a headwind, reducing weight, or departing VFR and picking up the clearance once clear of the terrain. Compare your POH climb performance at the actual density altitude and weight against the required feet per minute this calculator gives you.

Climb Gradient Calculator: Feet per NM to Feet per Minute

Required rate of climb

Required gradient (ft/NM)

From the ODP, SID, or missed approach; 200 is the TERPS standard

Groundspeed in the climb (kt)

Groundspeed, not indicated airspeed: wind changes this number

Required climb – feet per minute

Grade – percent slope

Enter a gradient and groundspeed.

Gradient you're achieving

Rate of climb (fpm)

From the POH climb chart at your weight and density altitude

Groundspeed (kt)

Achieved gradient – feet per nautical mile

Enter your climb rate and groundspeed.

Required rate of climb (fpm) = gradient (ft/NM) × groundspeed (kt) ÷ 60. The standard 200 ft/NM departure gradient at 90 knots groundspeed is only 300 fpm; a mountain SID demanding 425 ft/NM at 100 knots wants 708 fpm, which is a real number for a loaded single on a warm day. Convert the chart's gradient into fpm before you take the runway, not after the trees get big.

The formula, and a worked example

A climb gradient is height gained per distance travelled over the ground. Since groundspeed in knots is nautical miles per hour, dividing by 60 turns it into miles per minute:

fpm = gradient (ft/NM) × groundspeed (kt) ÷ 60
gradient = fpm × 60 ÷ groundspeed (kt)

Example: the ODP requires 340 ft/NM to 6,000 ft and you'll climb at 95 knots groundspeed. 340 × 95 ÷ 60 = 538 fpm, sustained, all the way to 6,000. If the POH says your loaded airplane does 450 fpm at that density altitude, the procedure isn't flyable today as filed.

Quick reference: gradient to fpm

Gradient	60 kt GS	90 kt GS	120 kt GS	150 kt GS
200 ft/NM	200 fpm	300 fpm	400 fpm	500 fpm
300 ft/NM	300 fpm	450 fpm	600 fpm	750 fpm
400 ft/NM	400 fpm	600 fpm	800 fpm	1,000 fpm
500 ft/NM	500 fpm	750 fpm	1,000 fpm	1,250 fpm

Notice the slope: the faster you go, the more feet per minute the same gradient costs. Climbing at V_Y instead of a cruise climb isn't just tradition; it buys gradient.

Groundspeed, not airspeed

The gradient is measured over the ground, so wind moves the requirement. A 20-knot headwind on departure cuts your groundspeed and makes the same VSI reading worth more feet per mile; a tailwind departure off a mountain runway quietly raises the fpm you need. Get the groundspeed from the wind triangle calculator, or read it off the GPS in the climb and re-check the math with the second card above.

Where 200 ft/NM comes from, and when it isn't enough

Instrument departure design (TERPS) assumes an aircraft crossing the departure end at 35 ft and climbing at least 200 ft/NM. When terrain or obstacles need more, the ODP or SID publishes a higher gradient and the altitude it applies to, and that number is binding for the procedure. Two habits keep it honest:

Convert the published gradient to fpm at your planned groundspeed before departure, and write it on the plate or the kneeboard.
Check it against POH climb performance at the actual weight and density altitude, not the sea-level book number.

If the airplane can't make the number: different runway, a published visual climb over the airport, less weight, cooler air, or don't go yet. Hoping is not on the list.

Common Questions

Why does the gradient use groundspeed instead of airspeed?

A gradient is feet gained per mile over the ground. A headwind lowers groundspeed and makes the gradient easier at the same climb rate; a tailwind does the opposite. High density altitude hurts twice: less rate from the engine, more groundspeed for the same indicated speed.

Is 200 ft/NM a regulation?

It's the TERPS design assumption for instrument departures: obstacle clearance is built around at least 200 ft/NM from 35 ft over the departure end. A procedure that needs more publishes the higher number, and that published gradient is what you have to meet, to the stated altitude.

What if I can't meet the published gradient?

Change something real: another runway or departure, a published visual climb over the airport, less fuel or payload, cooler temperatures, or wait for a headwind. Departing VFR clear of terrain and picking up the clearance airborne can work where conditions genuinely allow it.

Related tools and guides

Density Altitude Calculator

The number that decides whether the POH climb chart is on your side today.

Heading & Groundspeed Calculator

The groundspeed this page's math depends on.

Descent & Glide Calculator

The same arithmetic pointed downhill: top of descent and glide range.

Performance is one of eight risk categories

FlightDecide checks density altitude, runway performance, and weight and balance for your specific aircraft and flight window, alongside weather and NOTAMs, and shows the numbers behind every call.

Get FlightDecide on the App Store

Educational tool for flight-planning practice. It is advisory only and not a substitute for your POH, current charts, an official briefing, or your own judgment as pilot in command (14 CFR 91.3). Sources: FAA Instrument Procedures Handbook (FAA-H-8083-16B), Ch. 1; FAA Order 8260.3 (TERPS); AIM 5-2-9. Last reviewed: August 26, 2026.