At a glance
～わけだ means "that's why", "no wonder" or "so it means". You use it when known facts lead logically to a conclusion, or when you finally understand the reason for something.
Verb / い-adj (plain form) + わけだ
な-adj / Noun + な + わけだ
彼は日本に10年住んでいたから、日本語が上手なわけだ。 He lived in Japan for 10 years, so no wonder his Japanese is good.
How to form it
わけだ attaches to the plain form. Past and negative forms go before わけだ.
| Attaches to | Form | Example |
|---|---|---|
| Verb | Plain form + わけだ | 行くわけだ / 行かないわけだ / 行ったわけだ |
| い-adj | Plain form + わけだ | 寒いわけだ / 寒くないわけだ / 寒かったわけだ |
| な-adj | な + わけだ (past: だった) | 便利なわけだ / 便利だったわけだ |
| Noun | な + わけだ (past: だった) | 休みなわけだ / 休みだったわけだ |
| Register | わけだ is casual or written. わけです is polite. | 上手なわけです |