Estimating magnitudes is central to life, as well as to mathematics. Symbolic estimates involve assigning symbolic numerals to nonsymbolic magnitudes (or vice versa), whereas nonsymbolic estimates refer to mapping between two nonsymbolic magnitudes. In general, estimates on both types of tasks become more accurate with age and among adults, are more accurate for smaller than larger magnitudes. However, children and adults show task‐specific biases in their estimates. Moreover, young children systematically over‐ or underestimate, especially concerning smaller magnitudes. In this article, I discuss potential explanations for children's estimation biases, considering children's familiarity with numerals, which enhances their ability to discriminate between numerals but seems to temporarily make their estimates in their familiar number range less accurate. I also consider developmental asynchronies in the production and comprehension of number words.