**The last digit in any number is referred to as the estimated digit.** In science, all other numbers are considered significant digits because they are precise measurements.

The last number in a measurement in science is simply an estimation. For example, if a metal rod measures slightly over 234 inches, the final measurement can be rounded so the answer is 234 instead of 234.2. The more significant numbers a digit has, the more precise the measurement. A significant number includes all non-zero numbers, all zeros that fall between two significant digits and all zeros that are to the right of a decimal point or to the right of a non-zero number.