I'm up early tomorrow so I have to sleep early tonight.
I have an early morning tomorrow so I must sleep early tonight.
「[明日](https://eikaiwa.dmm.com/uknow/questions/36265/)」→「Tomorrow」
「[朝が早い](https://eikaiwa.dmm.com/uknow/questions/6644/)」→「To have an early morning, To be up early」
「～ないといけない」→「Must ~, have to ~」
まとめて言いますと、
「I'm up early tomorrow so I have to sleep early tonight.」
＝明日の朝は早いから今日は早く寝ないと。
「I have an early morning tomorrow so I must sleep early tonight.」
＝明日の朝は早いから今日は早く寝ないと。
になります。
どちらでも使えます。
I must go to bed now because I have an early start tomorrow
I should hit the hay because I have to wake up early.
「早く[寝ないと](https://eikaiwa.dmm.com/uknow/questions/38675/)」の単語は英語で数々な表現があります:
-I have to sleep early
-I have to go to bed early
-Get my beauty sleep (“美しくなるために必要な[睡眠](https://eikaiwa.dmm.com/uknow/questions/59195/)”という意味を持つ単語)
- I have to hit the hay (“寝る”というよく使う単語)
「明日の朝は早い」は:
- I have an early start tomorrow (明日のスタート時間は早い)
- I have to get up/wake up early (早い時間に起きないと)
なお、会話の途中で言いたい時には
“Anyway...” (ともかく)
“I’d love to talk more but..” (もっと話したいが、)
を使うといいです！
I'm going to go to bed now because I have an early start in the morning
I have an early day tomorrow so I'll have to go to bed now
These are a couple ways where you can express this message. An early day or start means that you will wake up early and have to begin doing your daily activities sooner than usual. The person you are speaking to should understand. Normally, it's polite to not call someone after 9 in the night and before 9 in the morning.
I need to go to bed early today because I have to get up early tomorrow
I'm going to bed now, got to get up early tomorrow
"I need to go to bed early today because I have to get up early tomorrow"
"I'm going to bed now, got to get up early tomorrow"
Both of these expressions are good to convey the message. There is no popular or most used phrase in the U.S. as many use different ones and it's a preference. These expressions is what use most to say something like that. The only difference between the two expressions is that the first one is a proper and polite way of saying it and the second is more for a person of trust or that you know very well i.e. your bf/gf and such.
例文
"I need to go to bed early today because I have to get up early tomorrow"
明日の朝早く起きなければいけないので、今日は早く寝る必要がある
"I'm going to bed now, got to get up early tomorrow"
早く寝るつもりだ、明日は早く起きないといけないから
これらの表現は両方共言いたいことを上手く伝えることが出来ます。多くの人が異なる表現を使い、それは好みの問題なので、アメリカでは、人気がある又はよく使われるフレーズはありません。
これらの表現は、この状況を伝える時によく使われます。2つの表現の唯一の違いは、最初の表現は、適切で丁寧で、2番めの表現は、どちらかというと信頼している人又はとても良く知っている人に使います。例えば、恋人のような人です。
I have an early morning so I better head off to bed soon.
I'm calling it a night,I have an early morning.
There are a number of ways to politely explain that you need to goo to bed when having a conversation on the phone.You could say :
-I've got to go to bed now because I have an early start tomorrow
-I have an early morning so I better head off to bed soon.
-I have an early morning so I better head off to bed soon.
The best way to end of the conversation would be to also express how pleasant it was to have spoken to the other person"
-Thank you so much for the call
-It was nice catching up with you
電話で話している相手にもう寝ないといけないことを丁寧に伝える場合、いろいろな言い方ができます。例えば：
例文
-I've got to go to bed now because I have an early start tomorrow
明日は朝早いので、早く寝ないといけない
-I have an early morning so I better head off to bed soon.
朝が早いから、もう寝ないといけない
会話の最後には相手と話ができて良かったと伝えるといいと思います。
例文
-Thank you so much for the call
電話してくれて本当にありがとう
-It was nice catching up with you
あなたと話ができて良かった
I need to get some rest because I have an early start tomorrow.
To say you need "Z's" is a slang way to say you need sleep. "Z's" refer to the snoring sound made which is normally illustrated with ZZZ's. "Gotta go" is a common way to say you're in a hurry and need to go. Getting up at "the crack of dawn" implies that you have to get up just as the sun is rising. "I need to get some rest because I have an early start tomorrow" is a classic way to say you need to go and get rest.
"I need some Z's" は、寝る必要があるという意味のスラングです。"Z's" は、いびきの音を表します。イラストでは普通 "ZZZ's" と書かれます。
"Gotta go" は、急いでいて行かないといけないと伝える一般的な言い方です。
"Get up at the crack of dawn" は、太陽が上がるころに起きなければならないという意味合いです。
"I need to get some rest because I have an early start tomorrow"
（明日朝早いから少し休まないといけない。）
- これは、休まないといけないと伝える典型的な表現です。
シンガポール 
日本 
アメリカ合衆国 
南アフリカ 
イギリス 
