One vanilla bean equals about 1 to 3 teaspoons of vanilla extract, depending on the size of bean and brand of vanilla extract. Because there is no universal control over how vanilla extract is produced, some brands are stronger than others.
Vanilla beans range considerably in size and potency, and Tahitian beans are some of the largest and strongest. Use judgment to scale the vanilla flavor for any particular recipe. Store vanilla beans in an airtight container in a cool, dry and dark place to keep them fresh for up to two years. Vanilla beans are often used in high-temperature recipes that would destroy vanilla extract.