Calculator
How old will I be when my child is 18?
Enter your child’s birthday and the birthdays of the adults in their life to see everyone’s age when your child starts school, turns 18, turns 30 and more.
Inputs stay in this browser. A copied result link contains the details you entered, so share it only with people you want to see them.
How to read the timeline
Each row is a moment in your child’s life. Each column shows how old that person will be on that day, counted in completed years. The first row answers the reverse question: how old each adult was on the day your child was born.
Add a grandparent to see the ages that are easy to avoid thinking about. A grandfather who is 66 at the birth is 71 on the first day of school and 84 at the eighteenth birthday.
What to do with it
The table is plain arithmetic, but it is a good prompt. If a grandparent will be in their eighties when your child is old enough to ask real questions, record a few of the answers now. Ten minutes of a grandparent telling one story, in their own voice, is the kind of thing families wish they had.
Common questions
How do I work out how old I will be when my child turns 18?
Add 18 to the age you were on the day your child was born. If you were 31 at the birth, you will be 49 on their eighteenth birthday.
How old were my parents when I was born?
Enter your own birthday as the child and your parents’ birthdays as the adults. The first row shows their ages on the day you were born.
Ask for one story while you can.
Invite a grandparent to add a voice note or a letter to your family archive.