Beaufort Wind Scale
Convert a wind speed to the Beaufort scale number with a description of sea and land conditions, free online.
About this calculator
The Beaufort scale rates wind force from 0 (calm) to 12 (hurricane). Beaufort number B ≈ (v ÷ 0.836)^(2/3) with v in m/s. Force 6 (strong breeze, 39–49 km/h) makes umbrellas hard to use; force 8 (gale) breaks twigs; force 10+ causes structural damage.