Baby Blood Type Calculator
Possible child blood types from both parents' types.
What it does
ABO blood types follow simple dominant rules: A and B dominate O, while AB carries both. Each parent passes one of two gene copies, and the pair decides the child type from a fixed table.
The tool above takes both parents types. It returns possible and impossible child types with the Rh rule beside.
O children need O from both parents, which is why two O parents always make O babies. AB parents always pass A or B, so their children can never be O.
Rh factor travels on separate genes with positive dominating. Negative children need a minus copy from each parent, which is why two positives can still make a negative child.
How to use
- Pick each parent ABO type.
- Read possible types first.
- Check impossible types for paternity questions.
- Remember Rh inherits on separate genes.
Formula
- dominant
- A and B show with a single copy.
- recessive
- O shows only with two copies.
Rare Bombay phenotype and mutations break textbook tables. DNA testing settles real disputes, not calculators.
Worked example
Example: O and AB parents
Parent one O, parent two AB.
- O parent always gives O.
- AB parent gives A or B.
- Pairs: AO makes A, BO makes B.
- Children: A or B, never O or AB.
Reference table
| Parents | Possible | Impossible |
|---|---|---|
| O x O | O | A, B, AB |
| O x A | A, O | B, AB |
| O x AB | A, B | O, AB |
| A x B | A, B, AB, O | none |
| A x AB | A, B, AB | O |
| AB x AB | A, B, AB | O |
Limits
- Textbook genetics only. Rare variants differ.
- Parental genotypes unknown beyond types.
- Rh handled as a rule, not computed.
- Not a paternity test. DNA decides.
Common mistakes
- Assuming children match a parent type.
- Forgetting O hides inside A and B parents.
- Mixing Rh with ABO inheritance.
- Reading impossible as impossible for Rh too.
- Using calculators for legal disputes.
Try it yourself
Quick checks. Answers sit tucked under each question.
A x O parents?
A or O children. Never B or AB.
B x B parents?
B or O children. Never A or AB.
Questions
Can O parents have an A child?
No, barring rare variants. O x O makes O only.
Can AB parents have O children?
No. AB always passes A or B.
How is Rh inherited?
Separately. Positive dominates; negatives need minus from both parents.
What is the rarest type?
AB negative in most populations, under one percent.
Does blood type affect health?
Slight links exist for clotting and disease risk. Lifestyle dominates.
Can this prove paternity?
No. It excludes some men but DNA testing decides.