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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.