This blood type calculator determines the possible blood type of a person based on the blood groups of his or her parents. Below the form you can read more about blood antigens and determination and also about blood transfusions.

Parent 1
AOB: *
Parent 2
AOB: *

How does this blood type calculator work?

This tool is based on theoretical principles and helps you reveal your possible blood types according to your parents' blood types. You are asked to input the blood group of the biological mother and father plus mention for each of them whether it is RH positive or negative.

In the early 20th century, Karl Landsteiner noticed that red blood cells have different molecules on their surface and differentiated blood into types. Type A had A molecules, type B has B molecules and type O has neither molecule. With the discovery of the Rhesus system that classifies blood into Rh positive and Rh negative, nowadays there are eight different blood types amongst the population.

The presence or absence of different antigens determines immune reactions that must be taken in consideration in cases of blood donation. The universal red cell donor has Type O negative blood type. The universal plasma donor has Type AB positive blood type.

Blood Type Can donate blood to Can receive blood from
A+ A+   AB+ A+   A-   O+   O-
O+ O+   A+   B+   AB+ O+   O-
B+ B+   AB+ B+   B-   O+   O-
AB+ AB+ Everyone
A- A+   A-   AB+   AB- A-   O-
O- Everyone O-
B- B+   B-   AB+   AB- B-   O-
AB- AB+   AB- AB-   A-   B-   O-

How Is My Blood Type Determined?

Research carried out in Heidelberg, Germany by Ludwik Hirszfeld and Emil von Dungern in 1910 and 1911 showed that the ABO blood types are inherited.  Now it is known that blood type is inherited and doesn't change as a result of environmental influences during life.

ABO inheritance patterns

The ABO blood group system is determined by the ABO gene. The four blood groups, determined by this system: A, B, AB and O, arise from inheriting one or more of the alleles: A, B or O. The first two are codominant alleles while the last if often called silent. Each biological parent donates one of their two ABO alleles to their child. A mother who is blood type AB could pass either an A or a B allele to her offspring. A father who is blood type O can only pass an O allele to his offspring.

Parental blood groups Child's blood group
O and O O
O and A O or A
O and B O or B
O and AB A or B
A and A A or O
A and B O or A or B or AB
A and AB A or B or AB
B and B O or B
B and AB B or A or AB
AB and AB A or B or AB

Rhesus inheritance patterns

The Rh blood group system depends on the existence of two genes RHD and RHCE. Rh positivity or Rh negativity is determined by the presence or absence of the dominant Rh gene. The fact that the Rh gene is dominant means that whenever a person has it is considered positive even if only one of the parents has the gene. 

Parental Rh type Child's Rh type
Positive and Positive Positive or Negative
Positive and Negative Positive or Negative
Negative and Negative Negative

Finding out your blood type

Did you know you can easily find your blood type with only a few drops of blood? A drop of the blood to be tested is mixed with a serum containing anti- A antibodies. Another drop is mixed with serum containing anti- B antibodies. The agglutination of one of the drops will tell the blood's appartenance to one type. If the blood in contact with the anti-A serum agglutinates but not the other one means it contains A antigens and not B antigens so it is type A. If the blood in contact with the anti-B serum agglutinates but not the other one means it contains B antigens and not A antigens so it is type B. If the blood mixed with both serums agglutinates means there are both A and B antigens so it is type AB. If none of the blood mixed with both serums agglutinates means there aren't either A and B antigens so it is type O.

While blood types are 100% genetically inherited, the environmental influence can determine which blood types in a population will be passed on more frequently to the next generation. This is natural selection. According to the American Red Cross the rarest blood type is AB(-), B(-) and O(-) are also very rare, each accounting for less than 5% of the world's population.


1) Maton A, Hopkins J, McLaughlin CW, Johnson S, Quon Warner M, LaHart D, Wright JD. (1993) Human Biology and Health. Englewood Cliffs NJ: Prentice Hall.

2) Letsky EA, Leck I, Bowman JM. (2000) Chapter 12: Rhesus and other haemolytic diseases. Antenatal & neonatal screening (2nd ed.) Oxford University Press.

3) Table of blood group systems. (2008) International Society of Blood Transfusion.

07 Dec, 2014