What is a 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.

Visual reference for how the knot relates to other speed units. Each row links to the full converter for that pair.

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

• ✓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.