Blood Type Calculator

Find which blood types a child could inherit from two parents (ABO and Rh).

Parent 1 blood type	A
Parent 1 Rh	Positive
Parent 2 blood type	B
Parent 2 Rh	Positive

Parent 1 blood type

Parent 1 Rh

Parent 2 blood type

Parent 2 Rh

Possible child blood types

A+, A−, B+, B−, AB+, AB−, O+, O−

Not possible: none.

ABO possibilities

Type	Possible?
A	Yes
B	Yes
AB	Yes
O	Yes

About the Blood Type Calculator

ABO blood type comes from two alleles: A and B are codominant, O is recessive. A type-A parent may be AA or AO, so two type-A parents can have a type-O child. Rh-positive is dominant: two Rh-negative parents will have an Rh-negative child, while Rh-positive parents may carry a negative allele.

The formula

Combine one ABO allele and one Rh allele from each parent

Worked example

Example: Possible child blood types = A+, A−, B+, B−

Inputs: Parent 1 blood type: O; Parent 1 Rh: Positive; Parent 2 blood type: AB; Parent 2 Rh: Positive.
Formula: Combine one ABO allele and one Rh allele from each parent
Result: Possible child blood types = A+, A−, B+, B−

Things to keep in mind

Rare variants (such as the cis-AB and Bombay phenotypes) can produce unexpected results.

Questions people ask

Can parents with A and B have an O child?

Yes, if both carry an O allele (AO × BO).

Can a blood type prove paternity?

It can exclude, never prove; DNA testing is needed.