How to Use the Blood Type Inheritance Calculator

This calculator helps determine the possible blood type and Rh factor of a child based on the parents' blood types and Rh factors.

Select the blood type and Rh factor for both the mother and father, then click "Calculate" to see the probabilities.

How Blood Type Inheritance Works

Blood type is determined by the combination of alleles inherited from both parents. The ABO system and Rh factor are the two main systems used to classify blood types.

• Type A: Can have genotype AA or AO.
• Type B: Can have genotype BB or BO.
• Type AB: Has genotype AB.
• Type O: Has genotype OO.

The Rh factor is either positive (Rh+) or negative (Rh-).

Blood Transfer Table

Because of the existence of blood types, not every person's blood can be transferred to a person in need. The rules of blood transfer are:

• AB blood type: Can receive blood from everyone else but can only donate blood for other individuals with AB type.
• 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.
• O blood type: Can receive blood only from individuals with the same blood type. However, they can donate blood to individuals with all blood types.
• Rh+ blood type: Can donate only to individuals with Rh+ blood type, but can receive blood from both Rh+ and Rh-.
• Rh- blood type: Can donate to individuals with both Rh+ and Rh- blood types, but can receive blood only from Rh-.

Recipient ↓ / Donor →	O+	O-	A+	A-	B+	B-	AB+	AB-
O+	yes	yes	no	no	no	no	no	no
O-	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

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%

FAQs

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 O-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.