Unit Conversion: Length, Mass and Capacity
Lessons in this chapter
About Unit Conversion: Length, Mass and Capacity
Measurement in 4th grade is entirely about conversion: moving between units within a system, and seeing why one system is easier to calculate with than the other.
Convert Metric Length Units and Convert Metric and Customary Capacity Units rest on powers of ten. Kilo means a thousand, centi means a hundredth, milli means a thousandth, and once those prefixes are known the conversions are the place value shifts kids have been doing all year.
Convert Customary Length Units is the awkward one, and deliberately so. Twelve inches to a foot, three feet to a yard and 1,760 yards to a mile have no pattern, so each has to be remembered, and the contrast makes the case for the metric system better than any explanation.
Convert Metric Mass Units and Customary Weight Units completes the set. The rule that keeps kids out of trouble is to check the direction: converting to a smaller unit always gives a bigger number, so meters to centimeters multiplies. Knowing whether the answer should grow or shrink catches almost every conversion error.
All four lessons open as a 4th grade math worksheet in the page. Convert Metric Length Units, Convert Customary Length Units and Convert Metric and Customary Capacity Units each set conversion problems that are worked one at a time and scored as you answer them. They are free to try, with no login needed for your first 3.
Frequently asked questions
Convert Metric Length Units rests on the powers of ten behind kilo, centi and milli, so the conversions are the place value shifts kids have been doing all year. Convert Customary Length Units is the deliberately awkward one, since twelve inches to a foot and 1,760 yards to a mile follow no pattern, and Convert Metric Mass Units and Customary Weight Units and Convert Metric and Customary Capacity Units complete the set. The chapter sits in the Common Core domain Measurement and Data (4.MD).
Check the direction. Converting to a smaller unit gives a bigger number, so you multiply. Converting to a larger unit gives a smaller number, so you divide.
Kilo is a thousand, centi is a hundredth, milli is a thousandth. One prefix set covers length, mass and capacity, which is why metric conversions are all the same.
Because there is no pattern. Twelve inches to a foot, three feet to a yard and 1,760 yards to a mile all have to be memorized separately.
A thousand, the same as the number of milliliters in a liter and millimeters in a meter. The prefix does the same job everywhere.
Going the wrong way, so dividing when you should multiply. Asking whether the answer should be bigger or smaller first catches nearly all of them.