The Beaufort Scale or Beaufort Wind Force Scale is a system for estimating wind strengths without the use of instruments, based on the effects wind has on the physical environment. The behaviour of smoke, waves, trees, etc., is rated on a 13 point scale of 0 (calm) to 12 (hurricane).
The scale was devised in 1805 by the British naval Commander, later Admiral, Sir Francis Beaufort (1774-1875). A further set of numbers (13-17) for very strong winds were added by the US Weather Bureau in 1955The Beaufort Scale, as originally drawn up, made no reference to the speed of the wind and various attempts have been made to correlate the two.
The scale is not often used today as more direct methods are used by meteorologists to measure wind speed. However, it is still useful in estimating wind speeds, especially when anemometers are not available