Child blood type calculator: ABO and Rh inheritance

Choose the blood type and Rh factor of both parents — the calculator shows the probability of each blood type in the child, which types are impossible and whether Rh incompatibility is possible, with genotypes, gametes and Punnett squares.

How blood type is inherited

ABO is controlled by one gene with three alleles: Iᴬ, Iᴮ and i⁰. Everyone has two copies, one from each parent. Iᴬ and Iᴮ are codominant; i⁰ shows only in i⁰i⁰.

Rh+ is DD or Dd, Rh− is dd — so two Rh+ parents (Dd × Dd) have a ¼ chance of an Rh− child.

FAQ

What blood type will a child of A and B parents have?

Any of the four types is possible; exact chances depend on the parents' genotypes.

Can two O parents have an A child?

Not under normal inheritance; rare exceptions exist.

Can Rh-positive parents have an Rh-negative child?

Yes, if both are Dd: probability ¼.

What is Rh incompatibility?

An Rh-negative mother carrying an Rh-positive baby. It is detected by antibody tests and prevented with anti-D immunoglobulin.

Can blood type prove paternity?

No. Only a DNA test can.

Why is the child's type different from both parents?

The child gets one allele from each parent; the combination can give a new type.