Choosing a Sensible Unit

Which unit fits best for each: a dose of cough syrup, a glass of milk, the water in a large aquarium?

Think about the dose of cough syrup: A dose fits in a small spoon = Teaspoons (tsp)

Think about the glass of milk: A normal glass holds about $8$ fl oz, which is $1$ cup = Cups

Think about the aquarium: It holds many big jugs of water, so cups would give a huge number = Gallons (gal)

Answer: Cough syrup: teaspoons. Glass of milk: cups. Aquarium: gallons.

Gallons to Quarts

A farmer fills $3$ gallons of milk. How many quarts is that?

Find the rule: $1 \text{ gal} = 4 \text{ qt}$ = Each gallon is 4 quarts

Big unit to small unit, so multiply: $3 \times 4$ = Multiply by 4

Calculate: $3 \times 4 = 12$ = $12$ qt

Answer: $3 \text{ gal} = 12 \text{ qt}$

Fluid Ounces to Cups

A bottle of juice holds $32$ fl oz. How many cups is that?

Find the rule: $8 \text{ fl oz} = 1 \text{ cup}$ = 8 fluid ounces make 1 cup

Small unit to big unit, so divide: $32 \div 8$ = Divide by 8

Calculate: $32 \div 8 = 4$ = $4$ cups

Answer: $32 \text{ fl oz} = 4 \text{ cups}$

Cups to Pints (with a half)

You made $7$ cups of lemonade. How many pints is that?

Find the rule: $2 \text{ cups} = 1 \text{ pt}$ = 2 cups make 1 pint

Small unit to big unit, so divide: $7 \div 2$ = Divide by 2

Calculate: $7 \div 2 = 3.5$ = $3.5$ pt, which is $3$ and a half pints

Answer: $7 \text{ cups} = 3.5 \text{ pt}$

A Rough Link to Milliliters

An American recipe needs $2$ cups of water. About how many milliliters is that?

Remember the size of a cup: $1 \text{ cup} \approx 237$ mL = A cup is about a quarter of a liter

Multiply by the number of cups: $2 \times 237 = 474$ = $474$ mL

Make sense of the answer: $474$ mL is close to $500$ mL = About half a liter

Answer: $2$ cups $\approx 474$ mL, about half a liter

Mistake: Multiplying when going to a bigger unit: $12 \text{ cups} = 24 \text{ pt}$

Why: A pint is bigger than a cup, so you need FEWER pints than cups. Multiplying makes the number bigger, which cannot be right.

Correct: Small to big: divide. $12 \div 2 = 6$, so $12 \text{ cups} = 6 \text{ pt}$.

Mistake: Mixing up the 2s and the 4: writing $1 \text{ gal} = 2 \text{ qt}$ or $1 \text{ qt} = 4 \text{ pt}$

Why: The chain has three steps of 2 (cup, pint, quart) and one step of 4 (quart to gallon). It is easy to put the 4 in the wrong place.

Correct: The name helps: a quart is a QUARTER of a gallon, so $4 \text{ qt} = 1 \text{ gal}$ and $2 \text{ pt} = 1 \text{ qt}$.

Mistake: Treating fluid ounces and ounces as the same thing

Why: An ounce (oz) measures weight, a fluid ounce (fl oz) measures volume. A cup of feathers and a cup of honey have the same volume but very different weights.

Correct: For liquids and recipes, use fluid ounces: $8 \text{ fl oz} = 1 \text{ cup}$.

Mistake: Using a tablespoon when the recipe says teaspoon

Why: The abbreviations tsp and tbsp look alike, but a tablespoon is 3 times bigger.

Correct: Remember $1 \text{ tbsp} = 3 \text{ tsp}$. Big T (tbsp) is the big spoon.

Baking from an American Recipe

American recipes measure small amounts with teaspoons and tablespoons. If you only have one kind of spoon, you convert.

A recipe asks for $2$ tbsp of sugar. With a teaspoon you need $2 \times 3 = 6$ teaspoons.

Buying Milk in the US

In American shops milk comes in gallons, half gallons, quarts and pints. Converting helps you see how much you really get.

A family drinks $1$ quart of milk a day. A $1$ gallon jug lasts $4$ days, because $1 \text{ gal} = 4 \text{ qt}$.

Staying Hydrated in Sports

Water bottles and sports drinks in the US are labeled in fluid ounces. Converting to cups makes the amount easier to picture.

A $16$ fl oz bottle holds $16 \div 8 = 2$ cups of water.

Q: Is a fluid ounce the same as an ounce?

A: No. A fluid ounce (fl oz) measures how much space a liquid takes up (volume). An ounce (oz) measures how heavy something is (weight). For water they are close, but for other things they can be very different.

Q: Why is it called a quart?

A: Quart comes from the word for a quarter. A quart is one quarter of a gallon, which is why $4 \text{ qt} = 1 \text{ gal}$.

Q: Is a quart the same as a liter?

A: Almost, but not quite. $1 \text{ qt} \approx 946$ mL, so a quart is a little less than $1$ liter ($1000$ mL). For quick estimates you can think of them as about the same size.

Q: How can I remember the whole chain?

A: Draw a big G for gallon. Inside it draw 4 Q for quarts, inside each Q draw 2 P for pints, and inside each P draw 2 C for cups. Counting the letters shows $1 \text{ gal} = 4 \text{ qt} = 8 \text{ pt} = 16 \text{ cups}$.