# Mental Calculation

> Source: https://ollybritton.com/notes/random/mental-calculation/ · Updated: 2025-12-01

- [The Doomsday Algorithm](https://ollybritton.com/notes/random/doomsday-algorithm/)
- Mentally calculating logarithms: <https://worldmentalcalculation.com/how-to-calculate-logarithms/>
- Mentally calculating square roots: https://en.wikipedia.org/wiki/Square_root_algorithms#Heron's_method

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Olly Britton — https://ollybritton.com. Machine-readable index: https://ollybritton.com/llms.txt