cannot do without; indispensable; absolutely necessary
Expresses that something is essential or that one cannot manage without it. Often used with a noun marked by が or は.
See also: なくてはいけない
Experience is absolutely necessary for this job.
Attaches to the negative base (ない-stem) of a verb to express obligation or necessity. Equivalent to ～なければいけない, but more colloquial.
See also: なくてはいけない
You can't get by without money.
I have to submit the report by tomorrow.
It's time I must go.
なきゃ is an even more casual abbreviation than なきゃいけない, often dropping いけない entirely in quick speech.
ないといけない is a colloquial variant similar to なきゃいけない, used interchangeably in casual speech to express obligation.
Both 無くちゃいけない and なきゃいけない are casual contractions expressing obligation, but 無くちゃいけない derives from なくては while なきゃいけない derives from なければ.
Contraction of なければいけない (nakereba ikenai), where なければ is the conditional form of ない. The colloquial shortening drops れ and ば, resulting in なきゃ.