Choosing the right kite size for the combination of wind conditions and your body weight is a critical for safe and enjoyable kitesurfing. Getting overpowered is no fun at all and you might get hurt. If in doubt, use a smaller kite rather than larger kite.
The following table maps out weight vs. kite size for the ideal wind range (typically from around 16 to 25 knots). Remember this is only a guide!
If you are after a secondary kite for stronger conditions, typically choose a kite 3 m2 smaller than your normal kite in the above table. E.g. if you are 81 kg, your main kite could be an 11m and your "strong wind day kite" could be an 8m.
As you become more accomplished you can move up or down a kite size depending on wind strength and your preference. Getting a larger kite will give you more power, while choosing smaller will give you more safety when the wind spikes.
As a guide, Peter (87kg) uses:
While Stuart (75kg) uses:
The above wind ranges are for riders with over 1 year experience and at least 30 sessions logged.
Sam has contributed this formula that could assist you choosing the right kite size:
We don't recommend going out in wind greater than 40 knots.
You should not go out in wind speeds above 25 knots during your first year kitesurfing and have logged 30 sessions.
The power and characteristics of kites can vary between manufacturers and models. For example, some have a greater depower range than others, and therefore can have a larger safe wind range. Read your kite manual carefully and follow the manufacturer's recommendation on wind range.
A smaller board needs more wind to get planing compared to a larger board.
Seek expert advice about a kite model/brand that you are buying. All kites are not equal - power can vary between different kite brands/models of the same size.