Numbers
Basic Numbers Big Numbers
Numbers
1/2
Basic Numbers
1-999

There are few exceptions while counting from 1 to 999 but the structure remains the same: 

 1-911-1910-90100-900
1いち 
ichi
じゅういち
juuichi
じゅう
juu
ひゃく
hyaku
2nijuuninijuunihyaku
3sanjuusansanjuusanbyaku
4yonjuuyonyonjuuyonhyaku
5gojuugogojuugohyaku
6rokujuurokurokujuuroppyaku
7nanajuunanananajuunanahyaku
8hachijuuhachihachijuuhappyaku
9kyuujuukyuukyuujuukyuuhyaku

4 can be pronounced either yon or shi depending on what it's counting.

7 can be pronounced either nana or shichi as well.

さんじゅうなな 
sanjuu nana
37
3 x 10 . 7

ろくじゅういち
rokujuu ichi
61
6 x 10 . 1

 はっぴゃくにじゅうさん
happyaku nijuu san
823
800 . 2 x 10 . 3

Numbers
2/2
Big Numbers
1,000-1,000,000+

While there are a few exceptions for big numbers, the structure differs from english:

  • 10,000 (man) is a base unit in japanese instead of 1,000 in english
  • There is no word for million or billion in japanese
 100010,000100,0001,000,000
1せん
sen
いちまん
ichiman
じゅうまん
juuman
ひゃくまん
hyakuman
2nisennimannijuumannihyakuman
3sanzensanmansanjuumansanbyakuman
4yonsenyonmanyonjuumanyonhyakuman
5gosengomangojuumangohyakuman
6rokusenrokumanrokujuumanroppyakuman
7nanasennanamannanajuumannanahyakuman
8hassenhachimanhachijuumanhappyakuman
9kyuusenkyuumankyuujuumankyuuhyakuman

Remember to count in base unit of 10,000 (man) when counting big numbers

ひゃくにじゅうごまん よんせんななひゃくにじゅうはち
hyaku nijuu go man yonsen nanahyaku nijuu hachi
1,254,728
125 × 10,000 + 4,728