Sibling Age Gap Calculator
Calculate the exact age difference between siblings in years, months, weeks and days.
Calculate sibling spacing
Compare two siblings using exact dates of birth.
Why parents compare sibling age gaps
Families use sibling-gap calculations for school stages, childcare planning, birthdays, family timelines and simple curiosity. The result describes spacing only; it does not predict sibling closeness or development.
For babies born close together
When births are less than a year apart, the years–months–days display is more informative than a whole-year subtraction.
Privacy
Input values are processed by JavaScript in your browser. The calculator code does not submit them to a server or place them in the URL.
Frequently asked questions
Can I use this for twins?
Yes. Enter both birth dates. For twins born on the same date, the result is zero days because birth time is not collected.
Does a larger sibling gap mean siblings will be less close?
No. Closeness depends on personality, family life and shared experiences, not the number alone.
Are names required?
No. Names are optional and remain in your browser.