Top of Descent Calculator
Find where to begin your descent, how far and how long it will take, and the resulting gradient — from either a target descent rate or a descent angle. Add a distance to run a "will I make it" check.
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Why This Matters to Pilots
Starting a descent too late forces a steep, high-rate descent that is uncomfortable, hard to manage, and can bust altitude or crossing restrictions. Planning your top of descent lets you fly a stabilized, efficient profile at your chosen rate.
The 3:1 rule is a fast mental shortcut, but real descents are affected by groundspeed changes, winds, and aircraft drag. Computing the exact top of descent point removes the guesswork, especially in faster aircraft where a few miles of error translate to hundreds of feet.
Limitations
- This calculator computes a single continuous descent. It does not account for altitude restrictions at intermediate waypoints, step-down fixes, or published approach profiles.
- For instrument approaches, always use the published procedure altitudes and crossing restrictions.
- ATC may assign descent rates or crossing restrictions that differ from your planned profile.
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Frequently Asked Questions
This calculator is for educational and planning purposes only. Always refer to your aircraft's POH/AFM, current NOTAMs, and official weather briefings. No calculator is a substitute for pilot-in-command judgment or CFI guidance.
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