\( 2.1 g = \square mg \)

To convert grams to milligrams, you simply multiply by 1,000 since there are 1,000 milligrams in a gram. So, \( 2.1 \, g \) would be \( 2.1 \times 1000 = 2100 \, mg \). It's a straightforward conversion that comes in handy for everything from cooking to lab work! When dealing with unit conversions, a common mistake is to treat the conversion factors incorrectly or to forget to adjust for moving decimals. Always keep in mind: when converting from grams to milligrams, you multiply by 1,000, while converting from milligrams to grams, you divide by 1,000. This little trick will help you avoid any miscalculations!