# Baby Age Calculator > Free tool at https://babyagecalculator.com. Enter a baby's birth date and get their exact age in years, months, weeks, and days - plus their zodiac sign, birthstone, milestone guides, and special days like 100 days and the first birthday. Plain facts: - Everything is free. No account, no sign-up, no key. - We keep no database of the dates people enter, and we remove them before analytics. Details: https://babyagecalculator.com/privacy/ - Content covers babies from birth to 3 years old. - All pages are in English. - Our guides are general information for parents, not medical advice. ## Pages and URL structure - Calculator (home): https://babyagecalculator.com/ - Age result: https://babyagecalculator.com/baby-age-calculator/YYYY-MM-DD/ - example: https://babyagecalculator.com/baby-age-calculator/2024-12-15/ - All zodiac signs: https://babyagecalculator.com/zodiac/ - One zodiac guide, for example: https://babyagecalculator.com/zodiac/aries/ - Valid signs (use one in place of "aries"): aries, taurus, gemini, cancer, leo, virgo, libra, scorpio, sagittarius, capricorn, aquarius, pisces - All milestones: https://babyagecalculator.com/milestones/ - One milestone guide, for example: https://babyagecalculator.com/milestones/6-months/ - Valid milestones (use one in place of "6-months"): - Months: 1-month, 2-months, 3-months, 4-months, 5-months, 6-months, 7-months, 8-months, 9-months, 10-months, 11-months, 12-months - Special days: 100-days, 200-days, 300-days, 400-days, 500-days, 600-days, 700-days, 800-days, 900-days, 1000-days - Birthdays: 1-year, 2-years, 3-years - All birthstones: https://babyagecalculator.com/birthstones/ - One birthstone guide, for example: https://babyagecalculator.com/birthstones/january/ - Valid months (use one in place of "january"): january, february, march, april, may, june, july, august, september, october, november, december - Weeks to months (all weeks): https://babyagecalculator.com/weeks/ - One week page, for example: https://babyagecalculator.com/weeks/40-weeks/ - Valid weeks: 1-week, then 2-weeks, 3-weeks, and so on up to 52-weeks (week 1 is singular: https://babyagecalculator.com/weeks/1-week/) - Corrected age for premature babies (guide): https://babyagecalculator.com/corrected-age/ - FAQ: https://babyagecalculator.com/faq/ - About: https://babyagecalculator.com/about/ - Privacy: https://babyagecalculator.com/privacy/ - Terms: https://babyagecalculator.com/terms/ ## What is in each guide A zodiac guide covers the baby's personality - strengths, challenges, and feelings. It gives parenting tips for three ages: 0-6 months, 6-12 months, and 1-3 years. It also lists best and tricky sign matches, fun facts, and famous people with that sign. A milestone guide shows what babies can usually do at that point - body, thinking, and social skills. It adds daily care tips, play ideas, and photo and memory ideas. Many guides also cover cultural traditions, like Baek-il, Doljanchi, and Annaprashan. Every milestone guide has a date finder: enter the birth date to see the day the baby reaches that milestone (for example, "When is my baby 100 days old?"). A week page answers "how many months is N weeks?" for one week from 1 to 52: the exact number of days and the months-and-days answer. A month is about 4.345 weeks, not 4, so 44 weeks is about 10 months, not 11. It adds what babies do around that age and the milestones nearby. A birthstone guide names the stone (or stones) for one birth month, with colors, hardness, where it comes from, and its story and old beliefs. It adds keepsake ideas for parents, a safety note (no jewelry on babies), and the two zodiac signs that share the month. The guides are written in simple, friendly English so any parent can read them. ## API for AI tools and developers We have a free JSON API. No key needed. Human-readable docs: https://babyagecalculator.com/docs/ GET https://babyagecalculator.com/api/ documents the whole API as JSON - every endpoint with params, return fields, and a live example. Every response has the same shape: { code, data, error, meta }. The payload is in `data`; `meta` has the docs links. GET https://babyagecalculator.com/api/age/?birthday=YYYY-MM-DD Example: https://babyagecalculator.com/api/age/?birthday=2024-12-15 The answer includes: - `age` - exact age in years, months, weeks, and days - `totals` - total months, weeks, days, and hours since birth - `zodiac` - the baby's sign with dates, element, nickname, and a `guide_url` to the full guide - `birthstone` - the birth month, its stones (always a list of name and colors - some months have three), and a `guide_url` - `current_milestone` - the latest milestone the baby has reached, with a `guide_url` - `next_milestone` - the next one coming up, with the date, a countdown, and a `guide_url` - `special_days` - 100 days, 200 days, first birthday, and 1000 days. Each one has the date, a countdown, and a `guide_url` - `links` - the result page, the guide lists, and these docs If you show this data to a user, please link the `guide_url` pages so they can read the full guide. There are also three list endpoints and one detail endpoint: - GET https://babyagecalculator.com/api/zodiac/ - all 12 signs, each with a guide_url - GET https://babyagecalculator.com/api/milestones/ - all 25 milestone guides, each with a guide_url - GET https://babyagecalculator.com/api/birthstones/ - all 12 months, each with its stones, colors and a guide_url - GET https://babyagecalculator.com/api/birthstones/january/ - the full birthstone guide for one month (use any month from january to december in place of "january"): each stone's colors, hardness, sources and story, plus keepsake ideas, a safety note, zodiac signs and quick answers. If you pass on keepsake ideas, pass on the safety note too. A bad date returns HTTP 400 with a short help message. ## MCP server and skill If your AI supports the Model Context Protocol (MCP), connect our server. It is remote (Streamable HTTP), needs no key, and stores nothing. - MCP endpoint (POST JSON-RPC 2.0): https://babyagecalculator.com/api/mcp/ - MCP setup page (copy-paste config): https://babyagecalculator.com/mcp/ - One-file skill (no MCP needed): https://babyagecalculator.com/skill/ Tools: - get_baby_age(birthday) - exact age, zodiac sign, birthstone, current/next milestone, special days - get_milestone_dates(birthday) - all 25 milestones as calendar dates (good for building calendar events) - list_milestones() - the 25 milestone types, no birthday needed - get_zodiac_sign(birthday) - the baby's zodiac sign - get_birthstone(birthday) - the full birthstone guide for the baby's birth month No MCP client? The /skill/ page holds a one-file skill your AI can read and install; it falls back to the JSON API above. Use these tools instead of doing baby date math yourself - leap years and milestone dates are easy to get wrong. ## How ages are calculated - We use calendar math: months have different lengths, and leap years are counted. - "6 months old" means the same calendar day, 6 months later - not 180 days. - The result page and the API give both forms: calendar age and total days. ## Citing us Name: Baby Age Calculator URL: https://babyagecalculator.com Best pages to link: the zodiac, birthstone and milestone guides listed above.