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Teaspoon — Definition, Formula & Examples

A teaspoon is a small US customary unit of volume used mainly in cooking and medicine, equal to one-third of a tablespoon. It is abbreviated as "tsp" and holds about 5 milliliters of liquid.

In the US customary system, one teaspoon is defined as exactly 16\frac{1}{6} of a fluid ounce, which equals 148\frac{1}{48} of a cup. Equivalently, 1 tsp = 13\frac{1}{3} tablespoon ≈ 4.929 mL (often rounded to 5 mL).

Key Formula

1 tsp=13 tbsp=16 fl oz=148 cup1 \text{ tsp} = \tfrac{1}{3} \text{ tbsp} = \tfrac{1}{6} \text{ fl oz} = \tfrac{1}{48} \text{ cup}
Where:
  • tsp\text{tsp} = teaspoon — the smallest common US volume unit for cooking
  • tbsp\text{tbsp} = tablespoon — equals 3 teaspoons
  • fl oz\text{fl oz} = fluid ounce — equals 6 teaspoons
  • cup\text{cup} = cup — equals 48 teaspoons

How It Works

You use teaspoons to measure small amounts of ingredients like salt, vanilla extract, or baking powder. To convert teaspoons to tablespoons, divide by 3, since 3 teaspoons make 1 tablespoon. To convert teaspoons to cups, divide by 48, because there are 48 teaspoons in 1 cup. When a recipe calls for larger quantities, it is often easier to convert teaspoons up to tablespoons or cups.

Worked Example

Problem: A cookie recipe calls for 12 teaspoons of sugar. How many tablespoons is that?
Step 1: Recall the conversion: 3 teaspoons = 1 tablespoon.
3 tsp=1 tbsp3 \text{ tsp} = 1 \text{ tbsp}
Step 2: Divide the number of teaspoons by 3.
12÷3=412 \div 3 = 4
Step 3: Write the result with the correct unit.
12 tsp=4 tbsp12 \text{ tsp} = 4 \text{ tbsp}
Answer: 12 teaspoons of sugar equals 4 tablespoons.

Another Example

Problem: You need 1/2 cup of lemon juice. How many teaspoons is that?
Step 1: Recall that 1 cup = 48 teaspoons.
1 cup=48 tsp1 \text{ cup} = 48 \text{ tsp}
Step 2: Multiply 48 by 1/2 to find half a cup in teaspoons.
48×12=2448 \times \tfrac{1}{2} = 24
Answer: Half a cup equals 24 teaspoons.

Visualization

Why It Matters

Teaspoons appear constantly in everyday cooking and in dosing liquid medicine, so understanding this unit is a practical life skill. In elementary math classes, converting between teaspoons, tablespoons, cups, and fluid ounces builds fluency with fractions and multiplication. Nurses and pharmacists also rely on teaspoon-to-milliliter conversions when measuring doses.

Common Mistakes

Mistake: Confusing teaspoons (tsp) with tablespoons (tbsp) because the abbreviations look similar.
Correction: Remember that a tablespoon is 3 times larger than a teaspoon. The lowercase "tsp" is the smaller unit; "tbsp" (or sometimes "Tbsp") is the larger one.
Mistake: Assuming 1 teaspoon equals exactly 5 mL in US measurement problems.
Correction: One US teaspoon is approximately 4.93 mL. For cooking, rounding to 5 mL is fine, but for precise science or pharmacy work, use the exact value.

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