Qoo10 has a block chain coin system, this is a simple coin converter and saving from normal cash rate.
Just compare two products with different packed units, identify which one is cheaper per unit price.
Basic grocery calculator, it simply adds all my items and computes for the total sum.
Basic unix permission and umask calculator. This came in handy at times that I forget the permission values, or I used this just to double check some items for review.
Basic percentage calculator, once in a while I always compute for the percentage difference rate of increase or decrease of certain stats.
Computes for the aspect ratio based on the target height or width.