Pick both parents’ blood types to see which ABO and Rh types their child can and cannot have — real inheritance genetics, honestly framed.
How blood types are inherited
Your ABO type comes from two alleles, one from each parent — A and B are dominant, O recessive — which is why two type-A parents can have a type-O child if both quietly carry an O allele. Pick both parents’ types and this calculator works through every allele combination, returning the child types that are possible, the ones that are ruled out, and the Rh answer alongside.
How to use it
- Select each parent’s ABO type and Rh factor.
- Read the possible child types — and the impossible ones.
- Note why it’s a range: a parent’s hidden O allele can’t be seen from type alone.
The inheritance rules
A worked example
Type A × type O parents: the child can be A or O — never B, never AB. Two Rh-negative parents can only have Rh-negative children; any Rh-positive parent makes both outcomes possible, because Rh+ can hide a recessive negative allele. The famous surprise case — A × B parents — can produce all four types if both carry O.
An honest boundary
This is standard textbook inheritance, and it is not a paternity test: rare genetic events (the Bombay phenotype, cis-AB) create exceptions, and only laboratory testing settles anything that matters. Treat surprising results as a reason to ask a professional, never as an answer.