Why do aircraft use knots instead of mph or km/h?

The knot is tied to nautical miles, which map to degrees of latitude. 1 nautical mile = 1 arcminute, making navigation by charts and GPS naturally compatible.

What is a knot in km/h?

1 knot = 1.852 km/h exactly (by definition of the nautical mile = 1,852 m).

Knots to MPH Converter

1 knot (kn) = 1.15078 mph = 1.852 km/h exactly. Aircraft cruise at 450–550 kn; ships travel 12–25 kn.

Formula

mph = knots × 1.15078

Worked example

Aircraft cruising at 450 knots: 450 × 1.15078 = 517.9 mph.

Quick reference table

kn	mph
5	5.753892
10	11.507785
15	17.261677
20	23.015569
50	57.538923
100	115.077845
250	287.694613
450	517.850304

Unit definitions

Knot (kn)

The knot (kn) = 1 nautical mile per hour = 1.852 km/h = 1.15078 mph. Used in aviation and maritime navigation worldwide.

Mile per Hour (mph)

Miles per hour (mph) is the US and UK road and general speed unit.

Common use cases

Aviation: converting airspeed from knots to mph for US audiences
Sailing and maritime navigation
Weather: tropical storm and hurricane wind speeds
Military and commercial aircraft speeds

MPH to KPH KPH to MPH Meters per Second to KPH

Related guides

SI vs Imperial Units: A Complete Guide

Two major unit systems divide the world: SI (the metric system) and the imperial system. Engineers, scientists, and tradespeople encounter both daily. This guide explains where each system came from, what makes them different, when each is appropriate, and which conversions matter most in practice.

Frequently asked questions

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