The numbers
| Measure | About | Exact US value |
|---|---|---|
| 1 teaspoon | 5 mL | ⅓ tablespoon, 4.93 mL |
| 1 tablespoon | 15 mL | 3 teaspoons, ½ fl oz, 14.79 mL |
| 2 tablespoons | 30 mL | 1 fluid ounce |
| 16 tablespoons | 240 mL | 1 cup |
NIST rounds the US spoons to 5 and 15 mL for home cooking. Metric recipes use 5 and 15 mL spoons, so in practice US and metric spoons are interchangeable.
Abbreviations
Recipes write tablespoon as tbsp, Tbs or a capital T, and teaspoon as tsp or a small t. Mixing up T and t gives three times too much or too little, which matters most with salt and baking powder.
The Australian tablespoon
An Australian tablespoon is 20 mL, or 4 teaspoons. New Zealand, the UK and North America use 15 mL. If you measure an Australian recipe with a 15 mL spoon, you get 25% less of that ingredient. The teaspoon is 5 mL in all of these. See cup (US) for cups.