Blood Type Compatibility Calculator
Find blood donation and transfusion compatibility for all ABO and Rh types.
Shows O- as universal donor, AB+ as universal recipient, and full chart.
Blood type compatibility is determined by the ABO blood group system and the Rh factor — two independent genetic traits that together create 8 common blood types. Compatibility matters for blood transfusions, organ transplants, and pregnancy planning.
ABO System formula: Blood type is determined by antigens present on red blood cell surfaces and antibodies in plasma:
- Type A — has A antigens, anti-B antibodies
- Type B — has B antigens, anti-A antibodies
- Type AB — has both A and B antigens, no antibodies (Universal Recipient for red cells)
- Type O — has no ABO antigens, both anti-A and anti-B antibodies (Universal Donor for red cells)
Rh Factor:
- Rh+ (positive) — Rh antigen present on red cells (more common)
- Rh− (negative) — Rh antigen absent
Blood transfusion compatibility (red blood cells):
| Recipient | Can Receive From |
|---|---|
| O− | O− only |
| O+ | O+, O− |
| A− | A−, O− |
| A+ | A+, A−, O+, O− |
| B− | B−, O− |
| B+ | B+, B−, O+, O− |
| AB− | AB−, A−, B−, O− |
| AB+ | All types (Universal Recipient) |
Plasma compatibility is reversed: AB plasma can donate to all types; O plasma can only go to type O recipients.
Inheritance formula: Blood type is inherited from both parents. Each parent contributes one allele (A, B, or O). A and B are dominant over O; A and B are codominant with each other.
- Two O parents → child is always O
- One A parent (AO) + one B parent (BO) → child can be A, B, AB, or O
Worked example — inheritance: Mother is type A (AO genotype). Father is type B (BO genotype). Possible child genotypes: AO (type A), BO (type B), AB (type AB), OO (type O). Each outcome has a 25% probability — all four blood types are possible from this couple.
Rh disease in pregnancy: An Rh− mother carrying an Rh+ baby can develop anti-Rh antibodies. Subsequent pregnancies may be at risk. Rh immunoglobulin (RhoGAM) is given to prevent sensitization.