Blood Type Calculator (Child's Possible ABO and Rh Type)
Choose each parent’s ABO genotype and Rh genotype to see the child’s possible blood types.
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Blood Type Calculator (Child's Possible ABO and Rh Type) by TheCalcTools
How the Blood Type Calculator (Child's Possible ABO and Rh Type) works
The ABO gene has three alleles: A and B are co-dominant and both dominate O. Each parent passes one allele. A type A parent can be AA or AO, which changes the chances; choose the genotype if you know it, or try both.
The Rh factor works like a simple dominant gene: D (Rh positive) is dominant over d (Rh negative).
The formula
Worked example
Using the default values shown in the calculator:
| Parent 1 ABO genotype | BO (type B) |
|---|---|
| Parent 2 ABO genotype | AO (type A) |
| Parent 1 Rh genotype | Dd (Rh+) |
| Parent 2 Rh genotype | Dd (Rh+) |
- BO × AO: A 25%, B 25%, AB 25%, O 25%.
- Dd × Dd: Rh negative 25%.
Result:
| Type A | 25.0% |
|---|---|
| Type B | 25.0% |
| Type AB | 25.0% |
| Type O | 25.0% |
| Rh positive | 75.0% |
| Rh negative | 25.0% |
Frequently asked questions
Can two type O parents have a type A child?
Not under normal ABO inheritance. Rare exceptions (such as the Bombay phenotype or cis-AB) exist, and blood-group results should be confirmed by a lab.
Can this prove parentage?
No. Blood type can only rule out some combinations; DNA testing is used for parentage.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.