Determine blood type compatibility for transfusion, calculate possible child blood types from parental genetics, and view population frequency data.
The ABO blood group system, discovered by Karl Landsteiner in 1901, classifies blood into four main types based on the presence or absence of A and B antigens on red blood cell surfaces: Type A, Type B, Type AB, and Type O. Combined with the Rh factor (positive or negative), this creates eight common blood types that determine transfusion compatibility and play a role in pregnancy management.
Understanding blood type compatibility is crucial for safe blood transfusions. Receiving incompatible blood can trigger a severe hemolytic transfusion reaction where the recipient's antibodies attack the donated red blood cells, potentially causing kidney failure, shock, and death. Type O-negative blood is the universal red cell donor (compatible with all types), while AB-positive is the universal recipient.
This calculator provides complete compatibility information for all eight blood types, showing which types you can safely donate to and receive from. It also includes a blood type inheritance calculator that determines possible blood types for children based on parental blood groups using Mendelian genetics. The tool displays population frequency data and a full 8×8 compatibility matrix for comprehensive reference.
Blood-group rules are simple once written out, but they are easy to mix up in the moment. This page keeps ABO/Rh compatibility and inheritance possibilities together so the result can be reviewed as a quick educational reference before any real transfusion or prenatal decision relies on formal lab testing.
ABO Compatibility: Type O has anti-A and anti-B antibodies, Type A has anti-B, Type B has anti-A, Type AB has neither. Donor RBCs must not carry antigens that the recipient has antibodies against. Rh: Rh− recipients should only receive Rh− blood.
Result: A+ can donate to A+ and AB+. It can receive from O−, O+, A−, and A+.
Type A+ blood carries A antigens and Rh factor. It can be given to A+ and AB+ recipients (who don't have anti-A antibodies and are Rh+). It can receive from any type that doesn't carry B antigens: O−, O+, A−, and A+.
For red-cell transfusion, the key question is whether donor red-cell antigens would be attacked by antibodies in the recipient. That is why O-negative is treated as the most broadly compatible emergency red-cell donor type, while AB-positive can receive the widest range of common ABO/Rh red-cell combinations.
The inheritance table shown here is based on the common ABO alleles and a simplified Rh-positive versus Rh-negative model. It is useful for classroom genetics and family blood-group possibilities, but it does not account for rare blood-group systems or unusual serology.
Real transfusion safety depends on formal blood typing, antibody screening, and crossmatching performed by the laboratory. This page is a compact reference for common ABO/Rh rules, not a substitute for transfusion-service workflow.
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This page models basic red-cell compatibility using the ABO and Rh(D) systems only. It also uses simplified Mendelian inheritance rules for ABO and Rh to show possible child blood groups from parental types. The output is educational and does not replace laboratory typing, antibody screening, or full pre-transfusion crossmatching; rare phenotypes and non-ABO/Rh antibodies are outside the scope of the calculator.
O-negative (O−) is the universal red cell donor because O cells lack A and B antigens, and Rh− is compatible with both Rh+ and Rh− recipients. It is much less common than O-positive, which is why O− units are usually conserved carefully for emergency use.
AB-positive (AB+) is the universal recipient for red blood cells because AB individuals have no anti-A or anti-B antibodies, and Rh+ can receive both Rh+ and Rh− blood. Use this as a practical reminder before finalizing the result.
No. Two type O parents (genotype OO × OO) can only produce type O children. All other ABO types require at least one A or B allele from at least one parent.
When an Rh− mother carries an Rh+ fetus, she may develop anti-Rh antibodies that could attack the fetus's red blood cells in subsequent pregnancies (hemolytic disease of the newborn). RhoGAM injection prevents this sensitization.
The ABO gene has three alleles: I^A, I^B, and i. A and B are co-dominant over O (i). Each person inherits one allele from each parent. Rh factor is determined by a separate gene (RHD).
Among the common ABO/Rh types, AB-negative (AB−) is generally treated as the rarest. There are even rarer blood groups outside the basic ABO/Rh system, such as Rh-null.