～のだから — After all; since | JLPT N3 grammar

Meaning

Use it when A is a real fact the listener knows or should accept, and B is the speaker's conclusion, judgment, intention, advice, or request. It is not for neutrally presenting a completely new reason and can sound pressuring.

Formation

V／い-adjective plain form＋のだから
な-adjective／N＋なのだから

When to use it

Where to use it: It fits persuasion and a natural conclusion: 'your leg is injured, so leave the bag to me,' or 'we came this far, so let's see this too.'
Where not to use it: Do not use it when the listener does not know A and you are merely reporting the reason for the first time; avoid it when the reminder could sound reproachful.

Examples

20 sentences

明日あしたはN3の試験しけんなのだから、今夜こんやはゲームを早めはやめにやめよう。
The N3 exam is tomorrow, after all, so let's stop gaming early tonight.
せっかく京都きょうとまで来きたのだから、朝あさの竹林ちくりんも歩いあるいてみたい。
Since we have come all the way to Kyoto, I want to walk through the bamboo grove in the morning too.
あなたは足あしをけがしているのだから、重いおもい荷物にもつは私わたしに任せまかせてください。
Your leg is injured, so please leave the heavy luggage to me.
もう子どもこどもではないのだから、自分じぶんの失敗しっぱいを人ひとのせいにしてはいけない。
You are no longer a child, so you must not blame other people for your mistakes.
電車でんしゃが止まっとまっているのだから、会社かいしゃに遅れるおくれるのは仕方しかたがない。
The trains are stopped, so being late for work cannot be helped.
本気ほんきで店みせを開きひらきたいのだから、まず一週間いっしゅうかんだけ屋台やたいをやってみよう。
Since you truly want to open a shop, let's first try running a street stall for one week.
この猫ねこは十七歳じゅうななさいなのだから、高いたかい棚たなに無理むりに登らのぼらせないで。
This cat is seventeen years old, so do not make it climb a high shelf.
約束やくそくしたのだから、雨あめでも必ずかならず迎えむかえに行くいく。
I made a promise, so I will come to meet you even if it rains.

12 more examples

海うみがこんなに澄んすんでいるのだから、少しすこし潜っもぐってみませんか。
The sea is this clear, so why don't we try diving for a while?
皆みんなが待っまっているのだから、もう一度いちどだけ舞台ぶたいに戻っもどってください。
Everyone is waiting, so please return to the stage just one more time.
明日あしたは試験しけんなのだから今日きょうは早くはやく寝ねましょう
Since there is an exam tomorrow, let's go to bed early today.
もう約束やくそくしたのだから必ずかならず行っいってください
Since you have already promised, please make sure to go.
初めてはじめてなのだから間違えてまちがえても大丈夫だいじょうぶです
Since this is your first time, it is all right to make mistakes.
時間じかんがないのだから急ぎいそぎましょう
Since we have no time, let's hurry.
せっかく日本にほんに来たきたのだからいろいろな所ところを見たいみたいです
Since I have come all the way to Japan, I want to see different places.
自分じぶんで決めたきめたのだから最後さいごまでやります
Since I decided for myself, I will see it through.
この部屋へやは静かしずかなのだからここで勉強べんきょうしよう
Since this room is quiet, let's study here.
外そとは寒いさむいのだからコートを着てきてください
Since it is cold outside, please put on a coat.
みんなが待ってまっているのだから早くはやく行こういこう
Since everyone is waiting, let's go quickly.
まだ子どもこどもなのだから少しすこし手伝っててつだってあげましょう
Since the child is still young, let's help a little.

Important notes

B naturally contains a judgment, hope, intention, or appeal to the listener, unlike the formal causal patterns.

Common mistakes

Nouns and な-adjectives require な: 学生なのだから, 大切なのだから.
Do not use it as an impersonal news explanation; it carries the speaker's stance and assumes A as shared fact.

Check yourself

Pick the translation of each sentence. The wrong options translate similar patterns, so watch the grammar rather than the words.

Sentence 1: 海うみがこんなに澄んすんでいるのだから、少しすこし潜っもぐってみませんか。 Because of heavy snow, the airport has been closed since morning.I will not go because it is raining.The sea is this clear, so why don't we try diving for a while?
Sentence 2: せっかく日本にほんに来たきたのだからいろいろな所ところを見たいみたいです A signal failure caused the train to be delayed by thirty minutes.I will study because there is a test tomorrow.Since I have come all the way to Japan, I want to see different places.
Sentence 3: まだ子どもこどもなのだから少しすこし手伝っててつだってあげましょう Since the child is still young, let's help a little.I often come to this shop because it is close to the station.This explanation is complicated, so children cannot understand it.