Real genetics
Baby blood type calculator
Choose both parents' blood types to see which types your child could have.
Possible blood types
Not possible
"Possible" and "not possible" follow strict genetic rules. The percentages also depend on whether each parent carries a hidden O or Rh-negative gene, which a normal blood test does not show, so we estimate it from typical population frequencies.
How blood type is inherited
Your ABO blood type comes from two genes, one from each parent. Each gene is A, B or O. A and B are both dominant and O is recessive, so:
| Genes | Blood type |
|---|---|
| AA or AO | A |
| BB or BO | B |
| AB | AB |
| OO | O |
That is why two type A parents can have a type O child: if both are AO, each can pass on their O gene, and the child is OO. It also explains why a type AB parent can never have a type O child: they have no O gene to pass on.
The Rh factor (the + or −) works the same way with one dominant gene (D, Rh positive) and one recessive gene (d, Rh negative). Two Rh-positive parents can have an Rh-negative baby if both carry the hidden d gene. Two Rh-negative parents always have an Rh-negative baby.
Quick reference: parents' ABO types
| Parents | Child can be | Child cannot be |
|---|---|---|
| O + O | O | A, B, AB |
| O + A | O, A | B, AB |
| O + B | O, B | A, AB |
| O + AB | A, B | O, AB |
| A + A | A, O | B, AB |
| A + B | A, B, AB, O | none |
| A + AB | A, B, AB | O |
| B + B | B, O | A, AB |
| B + AB | A, B, AB | O |
| AB + AB | A, B, AB | O |
Things to know
- This is not a paternity test. Rare variants such as the Bombay phenotype or cis-AB can produce results that break the simple rules. Only DNA testing can confirm parentage.
- Rh in pregnancy matters. If the mother is Rh negative and the baby could be Rh positive, doctors usually offer anti-D treatment. Talk to your midwife or doctor; this page is not medical advice.
- Blood type does not decide personality. Our personality test is for fun only.