Formal:
* Nenda kulala: This is the most literal translation, meaning "Go to sleep". It's a polite and neutral way to say you're going to bed.
Informal:
* Nimechoka, naenda kulala: This translates to "I'm tired, I'm going to sleep". It's a more conversational way to say you're heading off to bed.
Other options:
* Ninaenda kupumzika: This means "I'm going to rest". It can also be used to indicate you're going to bed.
* Nimechoka sana, nataka kulala: This translates to "I'm very tired, I want to sleep". It emphasizes your tiredness and your intention to sleep.
You can also use the phrase "kwenda kulala" which means "to go to sleep". You could say "Nina kwenda kulala" meaning "I'm going to sleep".
Remember that the best way to say it depends on the context and your relationship with the person you're talking to.