Kilometres to Nautical Miles Converter

Convert kilometres to nautical miles (km to nm) for maritime and aviation distances

Kilometres (km)

Nautical Miles (nm)

Decimal Precision

Conversion Mode

Conversion Result

Quick Conversions

Click any value to convert instantly

1 km

= 0.5400 nm

5 km

= 2.6998 nm

10 km

= 5.3996 nm

50 km

= 26.9978 nm

100 km

= 53.9957 nm

500 km

= 269.9784 nm

Conversion Formula and Steps

Kilometres to Nautical Miles Formula

To convert kilometres to nautical miles:

Nautical Miles = Kilometres ÷ 1.852

Alternative formula:

Nautical Miles = Kilometres × 0.539957

Nautical Miles to Kilometres Formula

To convert nautical miles to kilometres:

Kilometres = Nautical Miles × 1.852

Step-by-Step Conversion Example

Example: Convert 25 kilometres to nautical miles

Step 1: Identify the distance in kilometres: 25 km
Step 2: Apply the conversion formula: 25 ÷ 1.852
Step 3: Perform the division: 25 ÷ 1.852 = 13.4989
Step 4: Round to desired precision: 13.50 nm

Key Fact: One nautical mile is exactly 1.852 kilometres. This international standard was established in 1929 and is based on one minute of latitude at the equator.

Kilometres to Nautical Miles Reference Table

Comprehensive conversion values for maritime and aviation navigation:

Kilometres (km)	Nautical Miles (nm)	Kilometres (km)	Nautical Miles (nm)
1 km	0.5400 nm	100 km	53.9957 nm
2 km	1.0799 nm	200 km	107.9914 nm
5 km	2.6998 nm	300 km	161.9870 nm
10 km	5.3996 nm	500 km	269.9784 nm
20 km	10.7991 nm	750 km	404.9676 nm
50 km	26.9978 nm	1,000 km	539.9568 nm

Maritime and Aviation Context

What is a Nautical Mile?

A nautical mile (nm) is a unit of distance employed primarily in maritime and air navigation. Defined as exactly 1.852 kilometres or 1,852 metres, the nautical mile is based on the Earth’s circumference and represents one minute of latitude. This geographical foundation makes it particularly valuable for plotting courses on nautical charts and aviation maps.

Why Maritime Navigation Uses Nautical Miles

Mariners and pilots prefer nautical miles because they align directly with the Earth’s coordinate system. One degree of latitude equals 60 nautical miles, simplifying distance estimation and course plotting on charts. This relationship between distance and position creates a natural framework for navigation at sea and in the air.

Kilometres vs Nautical Miles

Whilst kilometres serve general terrestrial measurement and road distances, nautical miles excel in marine environments and aviation. A nautical mile is approximately 15% longer than a standard kilometre (1 nm = 1.852 km), reflecting its basis in Earth’s geometry rather than arbitrary measurement standards.

Distance Comparison

1 Kilometre

54% of 1 nm

1 Nautical Mile

1.852 km

Speed Measurement: Knots

Ship and aircraft speeds are measured in knots, where one knot equals one nautical mile per hour. This pairing of distance and speed units creates consistency across maritime and aviation operations worldwide.

Common Distance Conversions

Maritime Routes

English Channel crossing: Approximately 34 km (18.4 nm) at its narrowest point
Gibraltar Strait: About 14.3 km (7.7 nm) at the shortest distance
Typical harbour approach: 5-10 km (2.7-5.4 nm) from sea buoy to dock
Coastal navigation zone: Up to 22 km (12 nm) from shore in UK waters

Aviation Distances

Airport traffic pattern: Usually 3-5 km (1.6-2.7 nm) from runway
Short-haul flight: 500-1,000 km (270-540 nm)
Medium-haul route: 1,500-3,000 km (810-1,620 nm)
Transatlantic crossing: Approximately 5,500 km (2,970 nm) from London to New York

Territorial Waters

International maritime law defines territorial waters in nautical miles. The UK territorial sea extends 12 nautical miles (22.2 km) from the baseline, whilst the exclusive economic zone (EEZ) reaches 200 nautical miles (370.4 km) offshore.

Frequently Asked Questions

How many kilometres equal one nautical mile?

One nautical mile equals exactly 1.852 kilometres. This international standard definition was adopted in 1929 and is based on one minute of arc along a meridian of the Earth.

Why is a nautical mile longer than a kilometre?

The nautical mile is approximately 85.2% longer than a kilometre (1.852 km vs 1 km) because they measure distance differently. The nautical mile derives from the Earth’s circumference and represents one minute of latitude, whilst the kilometre is a metric unit based on the metre, originally defined as one ten-millionth of the distance from the equator to the North Pole.

Do ships and aeroplanes use kilometres or nautical miles?

Ships and aeroplanes predominantly use nautical miles for navigation and distance measurement. Maritime charts, aviation maps, and international regulations specify distances in nautical miles. Speed is measured in knots (nautical miles per hour). This global standard facilitates consistent navigation across international waters and airspace.

How do I convert kilometres to nautical miles mentally?

For a quick mental approximation, divide the kilometres by 2 to get a rough estimate in nautical miles. For example, 100 km ÷ 2 ≈ 50 nm. The actual value is 53.996 nm, so this method provides a reasonable estimate. For more precision, divide by 1.852 or multiply by 0.54.

Are nautical miles used on land?

Nautical miles are rarely employed for terrestrial distances. Land-based navigation and road distances use kilometres (in countries using the metric system) or statute miles (in the UK and USA for road signs). Nautical miles remain specific to maritime navigation, aviation, and the definition of territorial waters.

What is the difference between a nautical mile and a statute mile?

A nautical mile (1.852 km) is longer than a statute mile (1.609 km). One nautical mile equals approximately 1.151 statute miles. Statute miles are used for land distances in the UK and USA, whilst nautical miles serve maritime and aviation purposes globally.

How does GPS display distances at sea?

Marine GPS devices typically display distances in nautical miles by default, as this aligns with nautical charts and maritime conventions. Most GPS units allow users to switch between nautical miles, kilometres, and statute miles in the settings, though nautical miles remain the standard for professional maritime navigation.