What these baby predictor calculators do
Every expecting parent wonders the same things. Will the baby have their father's brown eyes or their mother's blue ones? Will that newborn blonde fuzz stay blonde? How tall will they end up, when will they actually arrive, and what blood type will show up on the birth paperwork? These six calculators give you a structured, genetics-informed estimate for each of those questions in seconds.
Each tool works differently because each trait is inherited differently. The eye, hair and blood type calculators apply the dominance hierarchy geneticists have mapped for those traits. The height calculator uses the mid-parental height formula pediatricians have relied on for decades, and the due date calculator uses the same date-based rule (Naegele's rule) used in prenatal care. The gender predictor is openly folklore rather than science, and it's labeled that way throughout.
Why results are shown as probabilities, not answers
None of these tools return a single definite answer, and that's deliberate. Traits like eye and hair color involve multiple genes whose combined effect can't be read off a parent's appearance alone. A result showing 65% brown means that among many children born to parents with this genetic profile, roughly two out of three would be expected to have brown eyes — not that your particular child is "65% brown-eyed."
Two siblings with the same parents can end up with noticeably different eye color, hair color and even blood type. Inheritance is decided independently at each conception, so results can vary even within one family.
Accuracy and limitations
- Self-reported colors are subjective — one person's "hazel" is another's "light brown."
- Ancestry matters and isn't fully captured — allele frequencies vary substantially between populations.
- Adult appearance can mislead — hair especially darkens with age, so childhood color is a better input where known.
- Genotype isn't visible from phenotype — for hair, eye color and blood type, a parent's own appearance doesn't reveal every gene they carry.
- No consumer tool matches genetic testing — services analyzing dozens of pigmentation SNPs or a lab blood panel are far more precise than any calculator.
Content on this site is checked against NIH MedlinePlus Genetics, the CDC, and ACOG. Each calculator page lists its specific sources.
All six calculators run entirely in your browser. Nothing you enter is sent to a server, stored in a database, or linked to any profile — no account, no email, no tracking.
Frequently asked questions
Yes — all six tools are completely free with no registration, payment, or email required.
They reflect established inheritance patterns but are estimates, not guarantees. The height and due date calculators are the most evidence-based; the gender predictor is folklore and not accurate at all.
Yes. The eye, hair, height and blood type tools only need information about the parents, so you can use them at any point — including before conception.
Yes, all tools are fully responsive and work in any modern mobile or desktop browser without an app.
No. These are educational and entertainment tools. For anything involving genetic conditions or pregnancy planning, speak with a doctor or genetic counselor.