Australia's tablespoon holds 20mL, or four teaspoons. Almost everywhere else, a tablespoon is 15mL, or three teaspoons. Follow an overseas recipe with Australian spoons and you're adding a third more of everything you spoon in.
When Australia metricated its kitchen measures in the 1970s, the standards body settled on a 20mL tablespoon, a round four teaspoons, rather than adopting the 15mL (three-teaspoon) tablespoon already used in the UK, US, Canada, and most metric countries. The reasoning was consistency with the existing Australian dessertspoon and teaspoon sizes at the time, not a printing error, and it's been the legal Australian standard ever since.
The gap is exactly a third: 20mL versus 15mL is a 33% difference. For a pinch of spice, nobody notices. For raising agents in baking, like baking powder, bicarb, or gelatine, a third too much can be the difference between a cake that rises properly and one that collapses or tastes metallic.
| Where | Tablespoon | Teaspoons |
|---|---|---|
| Australia | 20 mL | 4 tsp |
| US, UK, Canada, NZ, metric-standard | 15 mL | 3 tsp |
| US teaspoon itself | 4.93 mL | – |