Required Descent Rate Calculator
Planning a descent comes down to a simple rate problem: how fast must an aircraft come down to lose a given altitude in the time available? This calculator divides the altitude to be lost by the time allowed and returns the required vertical speed in feet per minute, the unit shown on a vertical speed indicator. It is the building block behind the familiar top-of-descent planning that pilots do before beginning a let-down, and it works equally well for a quick mental check or a teaching example. Enter the altitude you need to lose, in feet, and the time you have, in minutes, and the tool returns the steady descent rate that would accomplish it, along with the equivalent feet lost per second. Real descents also depend on groundspeed, wind, air-traffic instructions and aircraft limits, so treat the output as the planning rate rather than a clearance to fly. The relationship is exact and linear: halve the time available and you double the descent rate that the geometry requires. Every figure is computed deterministically from the formula shown below, with a worked example that reconciles exactly to the calculator defaults so you can follow each step.
Required descent rate is altitude to lose / time available. To lose 35,000 feet in 20 minutes, the rate is 1,750.00 ft/min, or about 29.17 feet per second.
Required descent rate formula
Descent rate (ft/min) = altitude / time
altitude = feet to lose
time = minutes available
ft per second = ft per minute / 60
The relationship is linear: for a fixed altitude, the required rate rises as the time falls. This is the planning rate only and does not account for wind, groundspeed or aircraft limits.
Worked example
Suppose you need to lose 35,000 feet of altitude in 20 minutes.
- Descent rate: 35,000 / 20 = 1,750.00 ft/min
- Per second: 1,750.00 / 60 = 29.17 ft/sec
The required descent rate is 1,750.00 feet per minute, about 29.17 feet per second. These are the calculator's default inputs, so the result matches the widget exactly.
Required Descent Rate Calculator: frequently asked questions
How is required descent rate calculated?
It is the altitude you need to lose divided by the time available, giving feet per minute. For example, losing 3,000 feet in three minutes requires a 1,000 foot-per-minute descent. The same rate can also be derived from distance and groundspeed when planning a top of descent.
What is a comfortable descent rate?
For passenger comfort, many descents are flown at around 1,000 to 1,500 feet per minute, though aircraft and procedures vary. Very high rates can be uncomfortable and may exceed aircraft or operational limits. This calculator returns the rate the geometry requires; whether it is practical depends on the aircraft.
Does groundspeed affect the descent rate?
Groundspeed determines how the descent maps to distance over the ground, which is why pilots often plan a top of descent using a three-degree path and groundspeed. This tool solves the simpler time-based version: given the time you have, what vertical speed is needed.
What does the vertical speed indicator show?
The vertical speed indicator displays the rate of climb or descent in feet per minute, the same unit this calculator produces. Matching the indicated rate to the required rate keeps the descent on the planned profile.
Is this an official procedure?
No. This is a general planning calculation. Actual descents follow published procedures, air-traffic control instructions and aircraft flight manual limits. NASA publishes extensive aeronautics research and educational material on flight and the physics of motion.
Official sources
- Aeronautics and flight physics educational resources: US National Aeronautics and Space Administration (NASA). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.