Properties of a Pocket Calculator for Astronauts

[sa-penguin]

If you read "The Martian" by Andy Weir, there is a section on an LCD exposed to vacuum. It's not nice. I suspect OLED displays would suffer the same fate.

So, if you have a calculator as a backup, it better be decompression - proof. Either LED, or part of a spacesuit Heads Up Display (HUD).

If there's a vacuum inside your suit, you are beyond worrying about a calculator.