Beaufort & Newton
The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land.
The wind range of a kite can be estimated in Beaufort (Bft.); or in knots, miles per hour (mph) or kilometres per hour (km/h, kph).
Newton is the unit of force. One Newton will accelerate a bar of chocolate (102g).
The strength of kite lines can be measured in deca Newton (daN). 10kg ~ 9.807daN.
For example, a 60daN kite line will pull up to 62kg of weight or body mass.
Generally speaking the lower the strength the thinner the line.