To get the "right" ratio of tea to water depends on a lot of objective and subjective factors like your preference for the strength of the tea, the type of water, how long you let it brew, the time you agitate the tea leaves, and the temperature of the water. Generally, we think the mid strength of the tea is around 500ml (16.0 oz) (a typical bottled water size in the US) This Hiya bottle holds ~800mL (27oz) so you have the option to adjust the strength of the tea to your liking depending on how much water you use. In other words if you want a lighter flavor you can increase your water, or if you want it stronger, to decrease the amount of water. You can also increase the strength based on agitation. This means with the 27 oz bottle you can shake it more and still get the rich full flavor.