Omni Calculator logo

Blood Type Calculator

Created by Bogna Szyk and Łucja Zaborowska, MD, PhD candidate
Reviewed by Małgorzata Koperska, MD and Steven Wooding
Based on research by
Lisa A. Urry Michael L. Cain Steven A. Wasserman Peter V. Minorsky Jane B. Reece Campbell Biology, 11th edition (Mendel and the Gene Idea; The Chromosomal Basis of Inheritance); Pearson; 2017
Last updated: Jan 18, 2024


If you've ever wondered what a blood type is or what blood type will your baby have, make sure to check out this blood type calculator. You will be able to check what are the possible blood types for your child based on the information about the parents. Additionally, in this article, you will find a handy table that explains how the blood groups of donors and recipients influence the option of blood transfusion.

Are you currently expecting a baby? Take a look at the pregnancy weight gain calculator!

What blood type am I?

There are four main groups of blood: A, B, AB, and 0. Each of them contains different antigens (such as carbohydrates or proteins) on the membrane of red blood cells. Depending on the presence or absence of these antigens, as well as on the presence of specific antibodies in the blood plasma, it is possible to find out which blood group your blood belongs to.

The blood type is determined genetically – each person inherits it from their parents. As it is controlled by a single gene, each person has two alleles describing their blood group:

  • Blood type A: either AA or A0
  • Blood type B: either BB or B0
  • Blood type AB: alleles AB
  • Blood type 0: alleles 00

Alleles A and B are dominant, and the allele 0 is recessive. It means that only people with 00 alleles can have the blood type 0.

Our calculator takes into consideration an additional classification that divides blood into two groups: Rh+ and Rh-. They also describe the presence or absence of a particular antigen – in this case, the Rh(D) antigen. The negative allele is recessive, which means that two parents with a blood type Rh- will always have children with Rh- blood.

💡 Rh- mothers need to receive immunoglobulins in order to prevent hemolytic disease in the fetus and newborn. To know more, check out the IVIG dose calculator.

What blood type will my baby have?

Your child will receive one allele from each of their parents. For example, if your blood group is A, and your partner's is AB, you can calculate the probabilities for possible blood types as follows:

  1. Write down your blood type and accompanying alleles. As your blood group is A, you either have AA or A0 alleles.

  2. Your child will either inherit an A allele (75% chance) or 0 allele (25% chance).

  3. Write down your partner's blood type and accompanying alleles. As their blood group is AB, he has the genotype of AB.

  4. Your child will either inherit an A allele (50% chance) or B allele (50% chance) from your partner.

  5. Now, multiply the probabilities to obtain the chance for each blood group:

    • The chance that your child's genotype is AA is 75% × 50% = 37.5%.
    • The chance that your child's genotype is AB is 75% × 50% = 37.5%.
    • The chance that your child's genotype is A0 is 25% × 50% = 12.5%.
    • The chance that your child's genotype is B0 is 25% × 50% = 12.5%.
  6. Add the results for AA and A0 together. Do the same for the results for BB and B0.

    • The chance for A blood group is 37.5% + 12.5% = 50%.
    • The chance for B blood group is 12.5%.
    • The chance for AB blood group is 37.5%.

You can perform a similar analysis for the Rh+ or Rh- groups. All you need to do is follow the following scheme:

  • If both parents are Rh-positive, then there's a 93.75% chance for an Rh+ and a 6.75% chance for an Rh- blood type.
  • If both parents are Rh-negative, then there's a 100% chance for an Rh- blood type.
  • If one parent is Rh-positive and the other Rh-negative, then there's a 75% chance for an Rh+ and a 25% chance for an Rh- blood type.

Naturally, we encourage you to use the blood type calculator instead of calculating the probabilities manually 😀

Blood transfer table

Because of the existence of blood types, not every person's blood can be transferred to a person in need. We even created a separate blood donor calculator to help you avoid confusion when donating or receiving blood!

The rules of blood transfer are:

  • A person with an AB blood type can receive blood from everyone else but can only donate blood for other individuals with AB type.

  • A person with an A or B blood type can receive blood from everyone except AB and can donate blood to other individuals with the same type. They can also donate blood to people with type AB.

  • A person with a 0 blood type can receive blood only from individuals with the same blood type. However, they can donate blood to individuals with all blood types.

  • A person with an Rh+ blood type can donate only to individuals with Rh+ blood type, but can receive blood from both Rh+ and Rh-.

  • A person with an Rh- blood type can donate to individuals with both Rh+ and Rh- blood types, but can receive blood only from Rh-.

These rules are summarized in the table below.

Recipient ↓ / Donor →

0+

0-

A+

A-

B+

B-

AB+

AB-

0+

yes

yes

no

no

no

no

no

no

0-

no

yes

no

no

no

no

no

no

A+

yes

yes

yes

yes

no

no

no

no

A-

no

yes

no

yes

no

no

no

no

B+

yes

yes

no

no

yes

yes

no

no

B-

no

yes

no

no

no

yes

no

no

AB+

yes

yes

yes

yes

yes

yes

yes

yes

AB-

no

yes

no

yes

no

yes

no

yes

Can a child have a different blood type than both parents?

Neither of your parents has to have the same blood type as you. For example, if one of your parents was AB+ and the other was O+, they could only have A and B kids. In other words, most likely, none of their kids would share either parent's blood type.

What are the rarest blood types?

Some of the rarest blood types are B negative, AB positive, and AB negative. Here is a table of blood groups and what percentage of the population have them:

Blood group

% of population

O positive

35%

O negative

13%

A positive

30%

A negative

8%

B positive

8%

B negative

2%

AB positive

2%

AB negative

1%

FAQ

What is the child's blood type if both parents are B positive?

The child can have B or O blood type, which will most likely, be positive.

Nevertheless, the child's blood may be negative if both parents are heterozygotes (with Rh+ Rh- genotypes).

What blood type suits everyone?

O-negative blood can be given to everyone. This is because 0-negative blood cells do not contain any antigens that the immune system of a person with another blood type could label as a threat and launch a reaction.

Can 2 parents with type B blood have a child with blood type O?

Yes, it's possible. Two parents with type B blood can have BO alleles, so if each of them passes on O, the child will get the O blood type.

How do I determine the possible blood types of my child?

To list possible blood types of your kid:

  1. Write down your blood type and that of your partner.
  2. Determine what genotypes may stand behind your blood types:
    • A may be AA or AO;
    • B may be BB or BO;
    • AB is just AB; and
    • O is OO.
  3. Write down all the possible combinations that arise when you take one letter from your blood type and the other from your partner.
  4. These are the potential genotypes of the child. Work out blood types using the list from Step 2.
Bogna Szyk and Łucja Zaborowska, MD, PhD candidate
Mother blood type
A Rh+
Father blood type
AB Rh-
Chance for type A
50
%
Chance for type B
12.5
%
Chance for type AB
37.5
%
Chance for type 0
0
%
Chance for Rh+
0
%
Chance for Rh-
0
%
PhenotypeGenotype
AA0 or AA
BB0 or BB
ABAB
000
Punnet square for possible blood types
♂️\♀️A0AA
AAAA0AAAA
BABB0ABAB
Check out 26 similar hematology calculators 🆎
4Ts scoreAbsolute eosinophil countAbsolute lymphocyte count… 23 more
People also viewed…

Millionaire

This millionaire calculator will help you determine how long it will take for you to reach a 7-figure saving or any financial goal you have. You can use this calculator even if you are just starting to save or even if you already have savings.

Serum osmolality

The serum osmolality calculator computes serum osmolality and the osmotic gap from laboratory test results.

Significant figures

The significant figures calculator performs operations on sig figs and shows you a step-by-step solution!

Vaccine queue Australia

The Vaccine Queue Calculator for Australia estimates where you are in the queue to get your COVID vaccine based on your age, health, and job.