Convert Knot to Beaufort Scale (kn → Bft)

Converting knots to Beaufort is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in knots

   Start with the number of knots (kn) you want to convert.
2. 2
   Multiply by 0.514444

   The conversion factor from kn to Bft is 0.514444. Multiply your value by this number.
3. 3
   Read the result in Beaufort

   The result is your value in Beaufort (Bft).

Multiply the value in knots by 0.514444. For the reverse direction, multiply by 1.943845.

• ✓1 knot = 1.852 km/h = 1.151 mph.
• ✓Knots cannot be abbreviated "kt" in sailing — standard is "kn".
• ✓A 40-knot wind is storm-force — 74 km/h.

• ✗Reading 40 knots as 40 km/h in weather — 74 km/h is much stronger.
• ✗Using "knots per hour" — already a rate; it's just "knots".
• ✗Treating knot as a distance unit — it's always a speed.

What is the Knot?

The knot equals exactly one nautical mile per hour (1.852 km/h or 0.5144 m/s) and is the universal speed unit for ships and aircraft worldwide. The name derives from the historical practice of measuring ship speed by counting knots tied at regular intervals along a 'log line' that was let out over the stern of a ship — the number of knots that passed in a given time gave the speed. International maritime regulations, aviation flight plans, and weather reports for sailors all use knots. A typical cruise ship sails at 18–22 knots, container ships at 18–25 knots, and commercial airliners at 470–500 knots cruise speed. The knot relates to km/h (1 knot ≈ 1.852 km/h), mph (1 knot ≈ 1.151 mph), m/s (1 knot ≈ 0.514 m/s), and the nautical mile (1 knot = 1 nmi/h). Wind speeds in aviation are also given in knots.

• Ship speeds and ocean currents
• Aircraft airspeed and ground speed
• Marine weather (wind reports in knots)

What is the Beaufort Scale?

The Beaufort scale is an empirical wind-force scale ranging from 0 (calm) to 12 (hurricane), developed in 1805 by British Royal Navy Admiral Francis Beaufort. Originally designed for ships at sea, the scale was based on observed effects: 'How much sail can my ship safely carry?' Modern versions describe both observed effects on land and sea and corresponding wind-speed ranges. Force 0 is dead calm (under 1 km/h), Force 6 is 'strong breeze' (39–49 km/h, large branches in motion), Force 10 is a 'whole storm' (89–102 km/h), and Force 12 is hurricane (over 118 km/h). The conversion to numeric speeds follows v = 0.836 × Bft^1.5 m/s. Sailors, meteorologists, and shipping forecasts still use the Beaufort scale because its descriptive nature is intuitive: 'Force 8 gale' immediately conveys conditions to anyone familiar with the scale.

• Marine weather forecasts
• Sailing and offshore navigation
• Historical weather records