Date & time Age
Age in weeks calculator
Date of birth
On this date
Weeks old —
The same age, other ways
Exactly —
In months —
In days —
In hours —
Born on a —
Next birthday —
Days to go —
Turning —
Note Enter a date of birth
Completed weeks, remainder separate
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Weeks old is days divided by seven, rounded down. A baby born eight weeks and three days ago is described as eight weeks old — the remainder is stated separately rather than rounded.
How to count weeks old
1 Enter the date of birth.
2 Read the completed weeks.
3 The exact breakdown includes the leftover days.
4 Use corrected age for a preterm baby against developmental milestones.
Weeks are the working unit for roughly the first three months, because feeding, sleep and growth guidance is all published that way and because the changes are weekly rather than monthly. Health services generally switch to months at around twelve weeks. The convention is always completed weeks — a baby is eight weeks old for the whole of the ninth week, in the same way an adult is 36 until their birthday.
Questions
Days since birth divided by seven, rounded down to completed weeks.
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