Blood Type Calculator
Blood type is inherited through Mendelian genetics. This calculator predicts possible blood types for a child based on both parents' ABO blood types and Rh factors, with probability percentages for each possible outcome.
Blood type is determined by two gene systems: ABO and Rh. The ABO system has three alleles — A, B, and O — where A and B are codominant and both are dominant over O. Each person inherits one ABO allele from each parent. Type A blood can have genotype AA or AO, type B can be BB or BO, type AB is always AB, and type O is always OO. The Rh factor is determined by the presence (Rh+) or absence (Rh–) of the D antigen, controlled by the RHD gene. Rh positive (D allele) is dominant over Rh negative (d allele).
Since phenotype (what we see) does not always reveal genotype (genetic makeup), the calculator uses probability-weighted estimates. For example, a parent with type A blood could be AA (homozygous) or AO (heterozygous), and since AO is more common in most populations, this affects the probability of each child blood type. The probabilities shown assume that heterozygous genotypes are twice as likely as homozygous for A and B types.
This calculator provides educational estimates. Actual blood type must be determined through laboratory testing. The predictions are based on simple Mendelian inheritance and do not account for rare variants, mutations, or Bombay phenotype.