Child Blood Group Predictor
Select both parents' blood groups (ABO + Rh factor) to see the possible blood groups for a child.
What this blood group calculator does
This blood group calculator predicts possible child blood groups based on the blood groups of two parents. It uses standard ABO and Rh inheritance rules and returns all blood types that are genetically possible.
If you are wondering whether a child can be A+, O-, AB+, and so on, this tool gives a quick and practical answer. It is useful for education, curiosity, and basic genetics learning.
ABO and Rh factor: the two systems you need to know
1) ABO system
The ABO system has four phenotypes: A, B, AB, and O. They are determined by inherited alleles:
- A can come from AA or AO genotype.
- B can come from BB or BO genotype.
- AB comes from AB genotype.
- O comes from OO genotype only.
A and B are co-dominant, while O is recessive.
2) Rh system
Rh is usually shown as plus or minus:
- Rh+ means at least one positive allele is present.
- Rh- means both alleles are negative.
So, two Rh- parents can only have an Rh- child, while Rh+ parents may have Rh+ or Rh- children depending on their hidden genotype.
How the calculator determines possible child blood groups
Because many blood group phenotypes can hide more than one genotype (for example, A could be AA or AO), the calculator tests all valid parental genotype combinations. Then it combines:
- ABO inheritance possibilities, and
- Rh inheritance possibilities
Finally, it lists every child blood group that can occur from those combinations and separates out groups that are not possible.
How to use it
- Select blood group for Parent 1.
- Select blood group for Parent 2.
- Click Calculate.
- Read the possible and impossible child blood groups.
Use the Reset button to clear and start over.
Example scenarios
Example A: O- and O-
Two O- parents can only produce O- children. No A, B, or AB outcome is possible.
Example B: A+ and B+
This pairing can produce a wide range: A, B, AB, or O types, and both Rh+ or Rh- depending on genotype combinations.
Example C: AB- and O+
ABO outcomes can be A or B only (not O and not AB in this direct combination), while Rh can be + or - depending on the Rh genotype of the Rh+ parent.
Important limitations
- This is a genetics-based probability tool, not a diagnostic test.
- Rare blood group systems outside ABO/Rh are not included.
- It does not provide legal or medical proof of parentage.
- For pregnancy and transfusion decisions, always rely on laboratory testing and clinical guidance.
FAQ
Can this calculator confirm paternity?
No. It can only show whether a blood group combination is possible or impossible. DNA testing is required for confirmation.
Why can two Rh+ parents have an Rh- child?
If both Rh+ parents carry one positive and one negative allele, a child may inherit two negative alleles and become Rh-.
Is O- always a universal donor?
O- red cells are often used as universal donor red cells in emergencies, but transfusion practice is nuanced and should always follow clinical protocol.
Educational use only. For medical advice, diagnosis, and treatment, consult qualified healthcare professionals.