I have recently been looking to move jobs, and it's always difficult to gauge what gross income translates into actual take-home pay. I have been using another website to calculate this, but I find it a bit clunky and slow to use. I felt I could make something a little more fun by myself.
Disclaimer
All numbers are approximate, do not take these as fully accurate. Further more, these numbers make a lot of assumptions about you, namely:
You are under 65
You are not blind
You are national insurance Category A
Your student loan is Plan 1 or Plan 2
You have no other miscellaneous deductions
This is the case for me and probably 95% of the people I know, so I figured it isn't worth the effort or making a fully-flexible solution.