One of the the most important things to learn when studying a new language is the vocabulary for how to count. Being able to discuss quantities is a great skill to acquire on your journey to learn Japanese. In Japanese, depending what it is you are trying to count, there are different methods used. Things that are flat, long, wide, big or small all have different counters. For now we won't worry about that and will just focus on basic counting.
Once you feel confident with basic counting you can move on to practicing the counters used for people and objects.
To form numbers from 11~19, start with "juu" (10) and then add the number you need.
Twenty is "ni-juu" (2X10) and for twenty one, just add one (nijuu ichi).
There is another numerical system in Japanese, which is the native Japanese numbers.
The native Japanese numbers are limited to one through ten.
Japanese Numbers
| 0 | zero/rei | 零 |
| 1 | ichi | 一 |
| 2 | ni | 二 |
| 3 | san | 三 |
| 4 | shi/yon | 四 |
| 5 | go | 五 |
| 6 | roku | 六 |
| 7 | shichi/nana | 七 |
| 8 | hachi | 八 |
| 9 | kyuu/ku | 九 |
| 10 | juu | 十 |
| 11 | juuichi | 十一 |
| 12 | juuni | 十二 |
| 13 | juusan | 十三 |
| 14 | juushi | 十四 |
| 15 | juugo | 十五 |
| 16 | juuroku | 十六 |
| 17 | juushichi | 十七 |
| 18 | juuhachi | 十八 |
| 19 | juuku | 十九 |
| 20 | nijuu | 二十 |
| 21 | nijuuichi | 二十一 |
| 22 | nijuuni | 二十一 |
| etc | ||
| 30 | sanjuu | 三十 |
| 31 | sanjuuichi | 三十一 |
| 32 | sanjuuni | 三十二 |
| etc | ||
| 40 | yonjuu | 四十 |
| 50 | gojuu | 五十 |
| 60 | rokujuu | 六十 |
| 70 | nanajuu | 七十 |
| 80 | hachijuu | 八十 |
| 90 | kyuujuu | 九十 |
| 100 | hyaku | 百 |
| 150 | hyakugojuu | 百五十 |
| 200 | nihyaku | 二百 |
| 300 | sanbyaku | 三百 |
| 1000 | sen | 千 |
| 1500 | sengohyaku | 千五百 |
| 2000 | nisen | 二千 |
| 10,000 | ichiman | 一万 |
| 100,000 | juuman | 十万 |
| 1,000,000 | hyakuman | 百万 |
| 10,000,000 | senman | 千万 |
| 100,000,000 | ichioku | 一億 |
