Nan sai desu ka
How old are you?
CASUAL - BETWEEN YOUNG PEOPLE AND FRIENDS
'Sai' means 'years of age'. We always add the word 'sai' after the number when we're talking about age.
Nan sai? 
  • How old are you? (Casual)
Juu-san sai.
  • Thirteen (years old).
Juu-yon sai.
  • Fourteen (years old).
FORMAL - FULL SENTENCES
Nan sai desu ka?
  • How old are you?
(Watashi wa) juu-san sai desu.
  • I am 13 years old.
(Boku wa) juu-yon sai desu.
  • I am 14 years old.​​
AGES 1 - 10
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KYUU SAI
issai * (ichi + sai)
  • 1 year old
​ ​ni sai
  • ​2 years old
san sai
  • ​3 years old
yon sai
  • ​4 years old
go sai
  • ​5 years old
roku sai
  • 6 years old
nana sai
  • 7 years old
hassai * (hachi + sai)
  • 8 years old
kyuu-sai
  • 9 years old
jussai * (juu + sai)
  • 10 years old
The asterisked ages have a pronunciation change. The number gets 'mooshed' together with the word, 'sai'.
e.g. ichi + sai = is-sai; hachi + sai = has-sai
AGES 11 - 20
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JUU-YON SAI
juu-issai 
  • 11 years old
juu-ni sai
  • 12 years old
juu-san sai
  • 13 years old
juu-yon sai
  • 14 years old
juu-go sai
  • 15 years old
juu-roku sai
  • 16 years old
juu-nana sai
  • 17 years old
juu-hassai
  • 18 years old
juu-kyuu sai
  • 19 years old
hatachi / ni-juu-issai
  • 20 years old
'Hatachi'  or 20 years old, is traditionally the age of adulthood in Japan. 
To say ages over 20, find out how to say the number, then apply the rules for saying ages that you have learnt here.
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PRACTISE LANGUAGE FOR SAYING NAMES AND AGES ON QUIZLET