Child’s Blood Type Calculator – How Does It Work & FAQ’s

Most people believe that kids are truly similar to their parents. They mean that kids look and behave like their parents or have similar likings as their parents. Science suggests this is due to genes or the DNA the child inherits from its parents. A baby’s blood type is determined by the genes and blood type of his parents. Though determining the exact blood type of an unborn child is not possible, with the aid of a blood type calculator or a genetic calculator for baby, a list of possible blood types can be formed.

What is a Child Blood Type Calculator?

A child type calculator determines the probable blood types of a child for the ABO blood system based on his parents’ blood types. Human blood group classification is divided into two systems- the ABO system and the Rhesus system. The ABO system is divided into four broad blood groups- A, B, AB and O. Rhesus system has Rh-positive( ) and Rh-negative (-).  Blood types A and B have antigen A and B respectively on their surface. Blood type O has no antigen.  All blood types are either Rh positive ( ) or Rh negative (-), making it a total of 8 blood groups.  Through the child blood type calculator, based on the blood types of parents, probable blood types for the baby are suggested and a blood type probability chart is made.

How Does the Calculator Determine the Child’s Blood Type?

There are certain theoretical principles on which the blood type calculator or blood type predictor works.  By imputing the blood types of both the parents and using these theoretical principles, a baby blood type estimator reveals the probable blood types for the child. The parents’ blood type has to be inputted with their RH positive or negative values.

1. ABO Blood Group System

What It is:

The ABO blood group system is determined by the ABO gene. When the child inherits one or more A, B or O alleles from his parents, then the blood group A, B, AB or O is developed. O is a silent allele whereas allele A and B are co-dominant alleles. Each of the parents gives one allele to their child, out of their two alleles.

For example:

  • If both parents have an O blood type, then they can give only the O allele to their child, so the child will have O blood type.
  • Parents with blood type A can have a child with blood type A or O.
  • Parents with B blood group can have a child with B or O blood group.
  • With one parent having blood type A and the other having blood type B, the baby’s blood type can be A, B, AB or O.
  • With one parent having blood type A and the other having blood type AB, the baby’s blood type can be A, B or AB.
  • With one parent having blood type A and the other having blood type O, the baby’s blood type can be A or O.

2. Rhesus Blood Group System

What It is:

The Rhesus Blood group system is made of complex blood types discovered in 1940 by Landsteiner and Weiner. The Rh factor linked to blood can either be positive (+) or Negative (-) and, by adding this to the ABO blood system, the eight blood types are formed. The Rh antigen, also called the D-Antigen, is an important antigen found in the red blood cells. The presence or absence of a dominant Rh gene determines the Rh-Positive ( ) or Rh Negative (-) blood type.

For example:

  • With both parents having Rh-Positive ( ) the child can either have an Rh-Positive ( ) or Rh Negative (-) blood type.
  • Both parents having Rh Negative (-) blood types will have a child with Rh-Negative (-) blood type.
  • With one parent having an Rh-Positive ( ) blood type and the other having an Rh Negative (-) blood type, the baby’s blood type can be Rh-Positive ( ) or Rh Negative (-).

different blood types


1. Can a Child’s Blood Type Differ From His Parents?

A child can have a different blood type from his parents. In the case of parents having AB and O blood type, the child can have either blood type A or B, which is not same as the parents’ blood groups.

2. Does a Child’s Blood Type Depend on the Blood Type of Both Parents?

The blood type of the child depends on his parents’ blood types. The child’s blood group is made up of two alleles, one allele donated by each parent. Therefore, the blood type of the child depends on the blood type or the alleles that his parent carries. For example, if the father’s blood type is BO and the mother’s blood type is AO, the child’s blood type can be any of these-  A, B, AB or O.

3. Which Blood Type is the Rarest?

The rarest blood type is AB negative. Only 1% of Caucasians have this blood type and in African Americans, it is even rarer to find. O negative and B negative are also blood types which are rare to find, as less than 5% of people in the world have them.

4. What Blood Types Should Not Have Babies Together?  

Rh incompatibility is when a mother-to-be and father-to-be are not both positive or negative for the Rh factor. In this case, the mother’s body produces an auto-immune response that attacks the foetus or newborn’s blood cells as if they were a bacterial or viral invader.  

The ABO incompatibility occurs when:  

  • The mother-to-be is type O, and the baby is B, A, or AB  
  • The mother-to-be is type A, and their baby is B or AB  
  • The mother-to-be is B, and their baby is A or AB  

5. Can Two O-Positive Parents Have an A Positive Child?  

Two O Positive Parents will only have a child with type O blood. But it is technically possible for two O-positive parents to have an A-positive child if you consider the rule-breaking exceptions.    

6. Do Twins Have the Same Blood Type?  

Identical twins will have the same blood type, with a few very rare exceptions, because they were created from the same fertilised egg. But fraternal twins can have different blood types.    

7. Do All Siblings Have the Same Blood Type?  

No. Siblings don’t always share the same blood type. The genotype of both parents plays a role in defining the blood type of children. 

The probable blood type of the child can be determined through blood type calculator for parent and child. However, parents should remember that the blood types suggested by the calculator are probable and, in reality, the actual blood group may differ from the calculated ones. Therefore, to know the actual blood group, get the child’s blood tested by a health care professional.

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Aarohi Achwal holds a bachelor’s degree in Commerce and a master’s degree in English Literature. While working as an intern for an English daily, she realised that she likes writing above anything else. The idea of being heard without having to speak appeals to her. She likes to write research-based articles that are informative and relevant. She has written articles on pregnancy, parenting, and relationships. And she would like to continue creating content on health and lifestyle.