Calculate possible blood types of children based on parents' blood types
Each parent carries two alleles for the ABO gene, passing one randomly to their child. The A and B alleles are co-dominant, meaning both can be expressed simultaneously, while the O allele is recessive. This calculator cross-references both parents' possible allele combinations to determine every blood type outcome their children could inherit.
Knowing blood type inheritance is critical for safe blood transfusions and organ transplants, where mismatched types can trigger dangerous immune responses. During pregnancy, Rh incompatibility between mother and fetus may cause hemolytic disease of the newborn. Understanding family blood types also helps in paternity determination and forensic identification scenarios.
Your phenotype is the blood type shown on a test (A, B, AB, or O), but your genotype reveals the hidden allele pair underneath. Someone with type A blood could carry genotype AA or AO, and only genetic testing or family pedigree analysis can distinguish between them. This calculator shows all possible genotype combinations and their resulting phenotype probabilities.
Select each parent's known blood type and Rh factor from the dropdowns, then review the probability table generated for offspring. If a parent's exact genotype is unknown, the calculator assumes equal likelihood of heterozygous and homozygous states. For the most accurate predictions, enter any known genotype information and consult a genetic counselor for medical decisions.
Blood type is determined by multiple alleles - specifically, the ABO blood group system and the Rh factor. These follow Mendelian inheritance patterns but with some unique characteristics.
The ABO gene has three alleles: IA, IB, and i (or IO).
| Genotype | Blood Type | Antigens Present | Antibodies |
|---|---|---|---|
| IAIA or IAi | Type A | A antigen | Anti-B |
| IBIB or IBi | Type B | B antigen | Anti-A |
| IAIB | Type AB | A and B antigens | None |
| ii | Type O | No antigens | Anti-A and Anti-B |
The Rh factor is determined by a separate gene with two alleles:
Rh positive individuals can be DD (homozygous) or Dd (heterozygous). Rh negative individuals are always dd (homozygous recessive).
If an Rh-negative mother carries an Rh-positive baby, her immune system may produce antibodies against the baby's blood. This is usually not a problem in first pregnancies but can cause complications in subsequent pregnancies. Rh immunoglobulin (RhoGAM) is given to prevent this.
Type O negative (O-) is the universal donor - can donate to any blood type.
Type AB positive (AB+) is the universal recipient - can receive from any blood type.
No. Two parents with type O blood both have the genotype ii (homozygous recessive), so every child will inherit one i allele from each parent and will also be type O. If a child has a non-O blood type, at least one parent must carry an IA or IB allele.
The Rh factor is determined by the RHD gene. The D allele (Rh positive) is dominant over the d allele (Rh negative). A person is Rh positive if they have at least one D allele (DD or Dd) and Rh negative only if they are homozygous recessive (dd). Two Rh-positive parents who are both Dd carriers have a 25% chance of having an Rh-negative child.
Blood type is inherited through the ABO gene, which has three alleles: IA, IB, and i. Each parent passes one allele to their child. IA and IB are codominant (both expressed when present together, producing type AB), while both are dominant over i. A child's blood type depends on which combination of alleles they receive, and the Rh factor is inherited independently on a separate gene.