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Child Gender by Blood Renewal

Based on a popular theory, this calculator predicts the gender of a baby by comparing the biological “renewal cycles” of blood in both parents. According to the concept, blood in men renews every 4 years and in women every 3 years. The parent whose blood is “newer” at the time of conception is believed to pass on their gender to the child. While not scientifically proven, this method is widely used as a fun way to guess a baby’s gender.

Baby Gender Predictor Based on Blood Renewal

Input Fields
If enabled, the result will update automatically when you change any value.

Blood Renewal Cycle Formula

Formula
$$\text{Age Difference (mod)} = \begin{cases} \text{Father’s Age} \bmod 4 \\ \text{Mother’s Age} \bmod 3 \end{cases}$$

Whichever parent has the lower remainder (i.e. more recently “renewed” blood), their gender is considered dominant:

  • Lower remainder for father → Boy
  • Lower remainder for mother → Girl

If the remainders are equal, some believe twins or a random outcome is possible.


The blood renewal method is based on the idea that men’s blood is completely renewed every 4 years, while women’s blood is renewed every 3 years. To use this method, you only need the age of both parents at the time of conception. This tool calculates which parent had “fresher” blood and predicts the child’s gender accordingly. This method has no medical backing, but it’s a fascinating cultural approach used across Eastern Europe and Asia for gender guessing.