Uploaded October 2018 | Updated September 2026, 2 weeks ago

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In this quick video, I use the definition of integration/Riemann sums to derive the Stirling Approximation or the Stirling Formula, which is a way to approximate the factorial of a large number.

There are multiple ways to derive the Stirling Formula; I've just shown one of the simple ones here. The drawback is that this is a less powerful derivation; perhaps this could be a hint for a more rigorous proof in a later video???

Special thanks to James Mark Wilson for suggesting this video!

Questions/Requests? Let me know in the comments!

Pre-reqs: Basic Calculus (i.e. you should know what integration means).

Lecture Notes: drive.google.com/open?id=1uMzWmrJXWyeUXUTwBDnmyCwmO6ENRdEW
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ERRATA: At 4:25, evaluating the integral should actually give you NlnN - N + 1, but since N is large, I automatically neglected the '1'.