Blood Type Calculator — FAQ

Select a blood type to see its transfusion compatibility — who it can donate to and receive from — or enter two parents' blood types to see the blood types their child could have, based on standard ABO and Rh inheritance.

Yes, it's completely free with no sign-up, downloads, or limits. Use it as often as you like.

O negative (O−) is known as the universal red-cell donor because it carries no A, B, or Rh antigens and can be given to people of any ABO and Rh type. AB positive (AB+) is the universal recipient, able to receive red cells from any type.

ABO refers to the A, B, AB, and O blood groups, determined by which antigens are present on your red blood cells. Rh (Rhesus) is the positive/negative factor — Rh+ means the Rh antigen is present, Rh− means it is absent. Together they make up the common eight blood types: A+, A−, B+, B−, AB+, AB−, O+, and O−.

Each parent passes one ABO allele (A, B, or O) and one Rh allele to their child. The tool combines the parents' possible alleles — accounting for the fact that type A can be genotype AA or AO, and type B can be BB or BO — to show which blood types a child could inherit, and which are not possible.

No — it shows the possible outcomes and, where relevant, which types cannot occur. Actual inheritance depends on each parent's specific genotype, which a blood type alone does not fully reveal. A type-A parent could be AA or AO; only genetic testing can confirm which.

Yes. The rules for plasma donation are effectively the reverse of red-cell donation — AB is the universal plasma donor and O is the universal plasma recipient. This tool focuses on red-cell transfusion compatibility, which is the most commonly referenced context.

No. Your selections are processed directly in your browser and are never stored or sent to a server, keeping your information completely private.

Yes, the calculator is fully responsive and works on smartphones, tablets, and desktops. The compatibility chart scrolls horizontally on smaller screens rather than forcing the page wider, so all content remains accessible without overflow.

No. This tool is educational. Real transfusions involve cross-matching and additional testing by medical professionals. Always rely on qualified healthcare providers for any actual medical decision.