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 they align with latitude/longitude coordinates, making navigation simpler at sea and in the air.

A cruise ship travels at 20 knots. How fast is that?

20 knots = 23 mph or 37 km/h. That's a typical cruise ship speed—fast enough to cover distance, slow enough for fuel efficiency.

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](/speed/mph-to-knots/).

Knots to Miles per Hour (mph) Converter

Enter a value to instantly convert between speed units.

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. Knots account for Earth's curvature and are essential for navigation at sea and in the air. Land-based speeds use mph or km/h.

Source: NIST SP 811, Table B.8

Frequently Asked Questions

Real-World Examples

Sailboat cruising speed. Typical for small sailing vessels under normal wind conditions.

10 kn = 11.51 mph

Motorboat or small ship speed. Common for ferries, fishing boats, and fast leisure craft.

20 kn = 23.02 mph

Fast yacht or speedboat. Recreational vessel at high speed; still safe for maneuvers.

25 kn = 28.77 mph

Navy frigate or fast patrol boat. Military-grade speed; commercial ships rarely exceed 25 knots.

30 kn = 34.52 mph

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

Knots to Miles per Hour (mph) Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

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