Converting Units of Capacity (Fluid Ounces, Cups, Pints, Quarts, Gallons)

by Laurie Laurendeau on April 17, 2012

Once your child has learned about the U.S. measures of capacity (fluid ounces, cups, pints, quarts and gallons), he will be ready to begin converting between these units.  Be sure your child has had many opportunities to explore objects in the world around him that demonstrate the various units of capacity.  For example, when you say “gallon”, your child should be able to picture a large milk jug as a reference for the measure of a gallon.  If you say “fluid ounce”, he should be able to tell you that this is a very small measure, and that several fluid ounces would fit inside his glass of milk.

There is a very clever visual aid that will help your child see the association between the units.  I did not come up with this trick – I’m not sure who did, but I really like it!

  1. Draw a huge uppercase letter “G” on a sheet of paper.
  2. Next, draw 4 large uppercase “Q”s inside the “G”, 2 beside each other, the other 2 below.
  3. Next, draw 2 uppercase “P”s inside each letter “Q”.
  4. Finally, draw 2 uppercase “C”s inside each letter “P”.

Explanation: The large G represents a Gallon.  The 4 “Q”s inside the “G” stand for Quarts, as there are 4 Quarts in one Gallon.  The “P”s represent Pints, and there are 2 Pints in a Quart.  Finally, the “C”s represent Cups, as there are 2 Cups in a Pint.  You may have noticed that fluid ounces (fl. oz) are not on the visual aid.  There are 8 fl. oz in 1 Cup, but there is simply not room on the chart to put all 8 fl. oz, so you will have to tell your child this conversion.  Please note that these conversions are for U.S. units of capacity.  The UK measurements are slightly different!

Explain to your child how this visual aid helps to remember how many ex: pints are in a quart.  Next, show him that he can convert between any of the units by looking at the visual aid.  For example, if he wants to know how many pints are in a gallon, he simply counts up the number of pints total in the large “G”, which would be 8, therefore there are 8 pints in a gallon.

Try these:
1.  1 G = __ Q

2.  1 Q = __ P

3.  1 P = __ C

4.  1 C = __ fl. oz

5.  4 P = __ Q

6. 8 C = __ P

7. 12 C = __ Q

8.  2 G = __ Q

9. 16 C = __ G

10. 7 P = __ Q

Feel free to make up other conversion questions of your own!


  • As always, playing math games at home is a great way to reinforce math skills learned in school.
  • Have questions or ideas about this story?
  • Need help or advice about your child’s learning?
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