Understanding the Blood Type Calculator
A blood type calculator predicts the possible blood types a child could inherit based on the parents’ types. Blood type follows clear genetic rules, so while you cannot always predict a child’s exact type, you can determine which types are possible and which are ruled out.
How ABO inheritance works
The ABO system is governed by three gene variants: A and B are co-dominant, while O is recessive. Each parent passes one variant to the child. This means two type-A parents can have a type-O child if both carry a hidden O variant, and a child’s type is sometimes different from both parents’ — a common source of surprise that is perfectly normal genetics.
The Rh factor
Blood is also classified as positive or negative based on the Rh factor. Rh-positive is dominant, so two Rh-positive parents can still have an Rh-negative child if both carry the negative variant. Rh status matters in pregnancy, where an Rh-negative mother carrying an Rh-positive baby may need preventive treatment, so it is worth knowing.
Tips & things to know
- •Two type-A or type-B parents can still have a type-O child.
- •The calculator shows possible types, not a guaranteed result.
- •Rh status is medically important during pregnancy.