Why do ships and planes use knots instead of mph or km/h?

Knots are nautical miles per hour—one nautical mile is 1.15078 statute miles (or 1,852 meters). Nautical miles are used because one nautical mile is about one minute of latitude, making navigation simpler at sea and in the air.

How do I estimate knots to mph mentally?

Rough estimate: multiply by 1.15 (or add 15%). Example: 20 knots × 1.15 = 23 mph. For precision, multiply by 1.15078.

A sailing race course is 12 nautical miles and I'm sailing at 8 knots. How fast am I going in mph, and when will I finish?

8 knots = 9.21 mph. At that speed, you'll cover 12 nautical miles (13.8 statute miles) in about 1.5 hours. Knots let you calculate time directly—one knot covers one nautical mile per hour by definition. For the reverse conversion, see mph to knots.

Knots to Miles per Hour (mph) Converter

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From

Precision4 dp

1 Knot = 1.1508 Mile per Hour

Key Formulas

Kilometer per Hour → Mile per Hour

mph = km/h × 0.621371

Mile per Hour → Kilometer per Hour

km/h = mph × 1.60934

Knot → Mile per Hour

mph = kn × 1.15078

Mile per Hour → Knot

kn = mph × 0.868976

Formula

mph = knots × 1.15078

One knot equals 1.15078 miles per hour. A knot is one nautical mile per hour—used in maritime and aviation contexts. The nautical mile was based on one minute of latitude, which makes knots convenient for navigation at sea and in the air. Land-based speeds use mph or km/h.

Source: NIST SP 811, Table B.8

Reviewed by the Convert Calc editorial team · Last reviewed: 2026-10-06 · see our methodology

Frequently Asked Questions

Real-World Examples

Boat speed example. 10 knots is about 11.5 mph.

10 kn = 11.51 mph

A vessel at 20 knots covers about 23 mph.

20 kn = 23.02 mph

Example speed of 25 knots, about 28.8 mph.

25 kn = 28.77 mph

Vessel speed example. 30 knots is about 34.5 mph.

30 kn = 34.52 mph

kmh to mph mph to kmh mph to knots ms to kmh kmh to ms

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