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Baby Age Calculator — Days, Weeks, Months from Date of Birth

Calculate baby age in days, weeks, months and years. Includes common developmental milestones (2 / 4 / 6 / 9 / 12 / 18 / 24 months) for reference.

How old is my baby?

Days

90

Weeks

12w 6d

Months

2

Years

0

Common milestones for context

2 monthsSocial smiles. Tracks faces. Coos.
4 monthsRolls front to back. Reaches for toys. Laughs.
6 monthsSits with support. First solids. Babbles.
9 monthsCrawls. Pulls to stand. Stranger awareness.
12 monthsFirst steps. First words. Hand-fed snacks.
18 monthsWalks independently. Vocabulary explodes.
24 monthsTwo-word phrases. Runs. Climbs.

Milestones are rough averages. Healthy babies hit them anywhere within a wide window. Discuss specific concerns with your pediatrician.

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Pregnant again? Use Due date for the new one, or Period predictor to track your cycle.

About this tool

Why parents track baby age in weeks

For the first year, infant development moves fast. Pediatricians use weeks (not months) for vaccinations, feeding charts and milestone tracking. This calculator gives you all four units (days, weeks, months, years) so you can use whichever your doctor asks for.

How to use the Baby Age Calculator

Takes about a minute. No signup, no download, your data stays in your browser.

  1. 1
    Open the tool. Scroll up to the Baby Age Calculator above — it loads instantly in your browser, no install needed.
  2. 2
    Enter your values. The fields come pre-filled with realistic defaults so you can see how it works — replace them with your own numbers.
  3. 3
    Read the result. The output updates instantly. Copy or share it — nothing is uploaded to a server, everything stays on your device.

Frequently asked questions

Common questions about the Baby Age Calculator.

Is the Baby Age Calculator free to use?

Yes. The Baby Age Calculatoron 7BusyBoss is completely free — no signup, no paywall, no usage cap.

Do I need to sign up to use the Baby Age Calculator?

No. The Baby Age Calculatorworks instantly in your browser — no account needed. Signing in with Google is optional and only unlocks features like saving favorites and higher AI build limits.

Does the Baby Age Calculator work on mobile?

Yes. Every tool on 7BusyBoss is mobile-responsive and works in any modern browser — Chrome, Safari, Firefox, Edge — on phones, tablets and desktops.

Is my data safe when I use the Baby Age Calculator?

Yes. The Baby Age Calculatorruns entirely in your browser — your inputs never leave your device unless the tool explicitly fetches public data (e.g. currency rates). We don't store the values you type.

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