Child's blood type calculator

Child's blood type calculator: what it is for

Choose the mother's and father's blood type and, if you know it, the ABO genotype of each. The tool combines the alleles of the ABO system and the Rh factor, shows the probability of each blood type for the child and indicates which ones are impossible under classical inheritance. When the mother is Rh− and the father Rh+, a warning about Rh incompatibility in pregnancy appears.

This tool is educational and does not replace medical tests or paternity tests.

How to use

1. Choose the mother's and father's type.
2. Enter the genotype, if you know it.
3. See the possible types and probabilities.

When to use it

• Study ABO system inheritance.
• Plan a pregnancy with the Rh factor in mind.
• Answer genetics questions.

Frequently asked questions

How is blood type inherited?

Each person has two alleles of the ABO gene, one from each parent. A and B are codominant and the O allele is recessive. Someone with type A can have genes AA or AO, someone with B can be BB or BO, AB is always AB and O is always OO. The Rh factor follows the same logic, with Rh+ dominant over Rh−.

How is the probability calculated without knowing the genotype?

When the genotype is not given, the tool weights the possibilities by the frequency of each allele in the population. If you know the genotype, for example because a grandparent is type O, choose it for an exact result.

Can parents with type O have a child with type A?

By classical inheritance, no: two type O parents only have type O children. Rare cases, such as the Bombay phenotype and gene variants, exist, and only a DNA test confirms paternity. This tool is educational and is not a paternity test.

Is it really free?

Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 are free.

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