Recent research suggests that both the accuracy and linearity of number estimations are a source of difficulty in mathematical learning. There is also a range of evidence to suggest that children in East Asia are typically mathematically precocious compared to Western peers. Bringing these strands of work together, we discuss number line estimations involving an ability match study of children growing up in the United Kingdom and China. This article confirms that the quality of children's number estimation is associated with some-but by no means all-early number problems. However, contrary to earlier studies, young Chinese children do not display more linear number scales in advance of (and potentially as a driver for) their math skills. Instead, their number estimations are not more accurate than those from an older Western sample with equivalent mathematical ability. The development of linearity in numerical representations takes a complex developmental path in multiple cultures. © The Author(s) 2011.