Knot

A knot (abbreviated kt or kts) is a unit of speed equal to one nautical mile per hour. Aviation and maritime navigation use knots as the standard measure of speed.

How It Works#

One nautical mile equals 1,852 meters, or about 6,076 feet. That makes it slightly longer than a statute mile (5,280 feet). Because nautical miles are tied to Earth's latitude grid, they simplify navigation calculations over long distances.

Speed in knots connects directly to distance in nautical miles. If an aircraft flies at 120 knots for one hour, it covers exactly 120 nautical miles. This clean relationship between speed and distance is why aviation adopted knots instead of miles per hour or kilometers per hour.

Instruments in the cockpit display airspeed in knots. The airspeed indicator (ASI) shows values like $V_{S}$ (stall speed), $V_{NO}$ (normal operating speed), and $V_{NE}$ (never-exceed speed), all in knots. Pilots also receive wind speed from air traffic control (ATC) in knots.

Example in Aviation#

A student pilot is flying a Cessna 172 on a cross-country flight. The aircraft cruises at 110 knots. ATC reports surface wind at the destination as "180 at 15 knots." The pilot uses both figures to calculate groundspeed and plan the approach. Every speed reference in that exchange, from cruise to wind, uses knots.

Why It Matters#

Knots are the universal language of aviation speed. Charts, performance tables, ATC communications, and cockpit instruments all speak in knots. A pilot who thinks in miles per hour must constantly convert, which adds workload and risk.

Understanding knots also helps pilots interpret aircraft performance data correctly. Rotate at the wrong speed because of a unit mix-up, and the consequences can be severe. Knots keep every pilot, controller, and dispatcher on the same page worldwide.

Key Takeaways#

• One knot equals one nautical mile per hour, not one statute mile per hour.
• Aviation uses knots for airspeed, wind speed, and groundspeed.
• Nautical miles align with Earth's coordinate grid, making navigation calculations cleaner.
• All critical speed limits (stall, cruise, never-exceed) are published in knots.
• ATC worldwide communicates wind and speed in knots, ensuring a common standard.