A Standard Serving
For traditional-grind kava root powder, a common serving is 2 to 4 tablespoons (roughly 10 to 20g) prepared in about 8 to 12 ounces of water. If you're new to kava, starting at the lower end, around 2 tablespoons, is a reasonable, cautious starting point rather than jumping straight to a full serving. See How to Prepare Kava for the full preparation process.
Why There's No Single "Correct" Dose
Kavalactone content varies meaningfully by cultivar, growing conditions, and how the product is processed, which means the same weight of kava powder from two different sources can produce noticeably different strength. Instant kava, since it's concentrated with the fiber removed, is generally stronger gram for gram than standard micronized or traditional-grind powder. Product-specific dosing instructions, when a vendor provides them, are usually more reliable than a generic weight-based rule, since they account for that specific product's actual kavalactone content. See Kava Forms Explained for how the different forms compare.
Multiple Servings in a Session
It's common for people to prepare two or three servings for an evening rather than just one, spacing them out and gauging how they feel between rounds rather than drinking everything at once. Since effects take 15 to 30 minutes to appear and continue building for a while after that, waiting to feel the first serving before deciding whether to have more is generally a more sensible approach than drinking in quick succession. See What Does Kava Feel Like? for the full effects timeline.
Factors That Change How Kava Affects You
Body weight, individual sensitivity, whether you've eaten, and cultivar all affect how a given amount of kava will feel. Drinking on an empty stomach generally produces stronger, faster effects than drinking after a meal. If you're new to kava, or trying a cultivar or product you haven't had before, starting conservatively and adjusting gradually over multiple sessions is a more sensible approach than assuming a fixed amount will always feel the same. None of this is medical advice, and if you have a liver condition, are pregnant, or take medications or alcohol, consult a doctor before drinking kava. See Is Kava Safe? A Complete Evidence-Based Guide.