Baby milestones and pediatric guidance are often tracked in weeks for the first few months, then in months afterward, which doesn't map neatly onto the years-and-months format used for adult ages. This tool gives the exact age in whichever unit matters most at that stage.
Enter a birthdate to instantly see the exact number of weeks old, months old, and total days — useful for tracking developmental milestones, vaccination schedules, or simply satisfying curiosity about exactly how old a little one is today.
The calculation is based on precise calendar math, so the figures stay accurate regardless of which months or leap years fall within the date range.
Because everything runs locally in your browser, results appear instantly and nothing you type or upload is ever sent to a server.
Bookmark this page if you expect to use this tool regularly — it loads fast and behaves the same way every time, with no account needed.
This kind of task shows up constantly in everyday writing, coding, design, and admin work, which is exactly why a dedicated, focused tool saves so much back-and-forth.
A tool that does one job well, without a cluttered interface or unrelated features competing for attention, tends to be faster to use than a heavier all-in-one app.
If you find yourself needing this conversion or calculation often, keeping this page open in a tab is usually faster than digging through a bigger software suite's menus.
Because there's no sign-up or installation step, you can jump straight from search result to working tool in a couple of seconds.
Frequently asked questions
Why track age in weeks instead of just months for babies?
Early developmental milestones and pediatric guidelines are often specified in weeks for the first few months of life, since changes happen quickly during that period.
Does this work for tracking pregnancy weeks too?
This calculates age from a birth date forward; pregnancy is typically tracked from the start of the last menstrual period using a dedicated pregnancy calculator instead.