Calculate possible child blood types
Select the blood type of each parent to estimate which blood types are possible for a child and the approximate probability of each outcome.
What this children's blood type calculator does
This blood type inheritance calculator helps you estimate the possible blood groups of a child based on parental blood types. It uses the two major inherited blood systems:
- ABO group: A, B, AB, or O
- Rh factor: positive (+) or negative (-)
The result shows which child blood types are possible and which are not possible under standard Mendelian inheritance. You can use it for family planning conversations, biology learning, and curiosity.
Quick genetics refresher
ABO inheritance basics
The ABO system comes from three possible alleles: A, B, and O. Each person carries two alleles (one from each parent).
- A and B are dominant over O.
- A and B are co-dominant with each other (together they produce AB).
- O is recessive and appears only when both alleles are O.
That is why two parents with blood type A can still have a child with type O (if both parents carry one O allele).
Rh factor inheritance
Rh positive usually acts as a dominant trait, while Rh negative is recessive. If both parents are Rh negative, the child will be Rh negative. If one or both parents are Rh positive, either positive or negative may be possible depending on hidden genotype combinations.
How to use the calculator
- Select blood type for Parent 1.
- Select blood type for Parent 2.
- Click Calculate.
- Review the probability table and the list of impossible outcomes.
The percentages are educational estimates based on common genotype assumptions when exact parental genotype is unknown.
Common examples
Example 1: O and O
When both parents are O, the child will be O only. Rh type still depends on each parent's Rh status.
Example 2: AB and O
A parent with AB can pass either A or B, and a parent with O can pass only O. So the child can be A or B, but not AB or O in ABO terms.
Example 3: A and B
This is one of the widest outcome combinations. Depending on hidden genotypes, the child may be A, B, AB, or O.
Important limitations
- This calculator is for education and general information, not diagnosis.
- Real-world genotype frequencies vary by population, ancestry, and family history.
- Rare blood systems and uncommon genetic variants are not included.
- Blood type alone cannot prove or disprove biological parentage with certainty.
For medical decisions, prenatal counseling, transfusion planning, or legal/paternity questions, consult a qualified professional and laboratory testing.
FAQ
Can this calculator tell my child's exact blood type?
No. It provides possible outcomes and estimated likelihoods, not certainties.
Why can one parent pair produce several blood types?
Because parents can carry hidden recessive alleles (especially O and Rh negative) that do not always show in their own blood phenotype.
Is the Rh factor independent from ABO?
For educational genetics models like this one, yes—ABO and Rh are treated as independently inherited, then combined into full blood types like A+, O-, or AB+.