For two right-handed parents, the chance of having a left-handed child is roughly 7% to 11% , with many sources clustering around about 1 in 10.

What that means

  • It is uncommon , but definitely not rare enough to be surprising.
  • Handedness is influenced by both genes and environment , so parent handedness only shifts the odds rather than determining the outcome.
  • In family studies, the estimate for two right-handed parents was about 9% in one large analysis and 11% in another study.

Simple example

If 100 couples are both right-handed, you might expect around 7 to 11 of their children to be left-handed.

Why it happens

  • Left-handedness does run in families, but it is not a simple inheritance pattern.
  • Studies suggest biological parent handedness matters more than adoptive parent handedness, which points to a genetic contribution.
  • Even so, the trait is complex, and researchers say it cannot be predicted perfectly from parents alone.

TL;DR: with two right-handed parents, the chance of a left-handed child is about 1 in 10 , give or take a few percentage points.