~回 is the neutral, default counter for a number of times or repetitions. It is what you use for concrete, countable occurrences - 三回会った (met three times), rounds of a game, sets in the gym, or frequency like 一週間に二回 (twice a week).
~度 tends to carry a more emotional or emphatic nuance and often refers to occasions rather than a plain tally. It is common in set expressions such as 何度も (over and over), 今度 (this time / next time), and もう一度 (one more time). Note that ~度 also means degrees of temperature and angles, but that is a separate use from counting times.
A handy guideline: when in doubt, ~回 is the safe choice for a straightforward count, while ~度 shines in fixed phrases and when you want to stress that something happened yet again.
~回 (times / occurrences)
A small っ appears after 1, 6, 8, 10 and 100; otherwise the reading is plain かい.
| No. | Kana | Kanji |
|---|---|---|
| 1 | いっかい | 一回 |
| 2 | にかい | 二回 |
| 3 | さんかい | 三回 |
| 4 | よんかい | 四回 |
| 5 | ごかい | 五回 |
| 6 | ろっかい | 六回 |
| 7 | ななかい | 七回 |
| しちかい | ||
| 8 | はっかい | 八回 |
| はちかい | ||
| 9 | きゅうかい | 九回 |
| 10 | じゅっかい | 十回 |
| 11 | じゅういっかい | 十一回 |
| 12 | じゅうにかい | 十二回 |
| 13 | じゅうさんかい | 十三回 |
| 20 | にじゅっかい | 二十回 |
| 21 | にじゅういっかい | 二十一回 |
| 100 | ひゃっかい | 百回 |
| 1000 | せんかい | 千回 |
| 10 000 | いちまんかい | 一万回 |
| How many | なんかい | 何回 |
~度 (times / occasions)
~度 is regular - there are no sound changes at all, just the number plus ど.
| No. | Kana | Kanji |
|---|---|---|
| 1 | いちど | 一度 |
| 2 | にど | 二度 |
| 3 | さんど | 三度 |
| 4 | よんど | 四度 |
| 5 | ごど | 五度 |
| 6 | ろくど | 六度 |
| 7 | ななど | 七度 |
| しちど | ||
| 8 | はちど | 八度 |
| 9 | きゅうど | 九度 |
| 10 | じゅうど | 十度 |
| 11 | じゅういちど | 十一度 |
| 12 | じゅうにど | 十二度 |
| 13 | じゅうさんど | 十三度 |
| 20 | にじゅうど | 二十度 |
| 21 | にじゅういちど | 二十一度 |
| 100 | ひゃくど | 百度 |
| How many | なんど | 何度 |
Check out other counters.