How to parse しなくちゃいけない

[alo]

Ok, so BunPro.jp is telling me that this form means “must do something”, like:

もっと文法うを勉強しなくてはいけない [する]
I must study more grammar

So, is it:
しない (to not do) --> しなくては (to not do て-form plus は)
–plus–
いけない (not going to)
–equals–
しなくてはいけない (not going to not do it = must do it) ???

[Belthazar]

しなくちゃ = しなくては = if (you) don’t do (it)

いけない = not good

しなくちゃいけない = if (you) don’t do (it), that would be bad = (you) should do (it).

[alo]

いけない = not good

Ah, that’s the bit I was missing. Thanks so much