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Convert Miles per Hour to Knots - Speed Converter

This converter transforms a speed value expressed in miles per hour (mph, statute miles per hour) into nautical knots (kn, nautical miles per hour). Knots are used in maritime and aviation contexts and are based on the international nautical mile.

The tool uses the internationally agreed definitions of the statute mile and the nautical mile so the mathematical conversion is deterministic. For critical uses (navigation, regulated reporting, instrumentation), follow the calibration and uncertainty guidance below and verify values against certified instruments or charts.

Updated Nov 20, 2025

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Methodology

Definitions: 1 statute mile is defined as exactly 1,609.344 meters. 1 international nautical mile is defined as exactly 1,852 meters. These exact definitions are used to compute the conversion factor.

Conversion practice and precision: the converter applies the exact metric-based definitions to compute an exact rational factor. Display precision should match the use case: two to four significant figures for general display, and more digits for engineering, scientific, or regulatory reporting. When used for navigation, include measurement uncertainty and round per the receiving system's requirements.

Calibration and compliance: for measurement instruments and reporting that affect safety or legal compliance, use instruments calibrated to nationally or internationally recognized labs (for example, ISO/IEC 17025 accredited labs). Follow guidance from standards bodies on measurement uncertainty (see citations).

Worked examples

1 mph = 0.8689762419 kn (commonly shown as 0.8690 kn when rounded to four decimal places).

60 mph = 60 × 0.8689762419 = 52.138574514 kn (displayed as 52.1386 kn for four decimal places).

100 mph = 86.89762419 kn (displayed as 86.8976 kn when rounded to four decimal places).

Key takeaways

This converter uses exact international definitions to convert mph to knots with a factor of approximately 0.8689762419. For casual use a few decimal places are sufficient; for regulated or safety-critical contexts follow calibration and reporting standards and include uncertainty estimates.

Further resources

Expert Q&A

Why is a nautical knot different from miles per hour?

A knot is one nautical mile per hour. A nautical mile (1852 m) is based on the Earth's meridian and historically tied to one minute of arc of latitude; a statute mile (1609.344 m) is a different length. Because these base lengths differ, their per-hour speed units differ by a fixed conversion factor.

How many significant digits should I use?

For general display use 2–4 significant digits. For navigation, meteorology, or engineering, match the precision required by procedures or instruments and include measurement uncertainty. High-precision applications may require carrying additional significant figures internally before final rounding.

Is the conversion exact?

The conversion uses exact international definitions for the statute mile and the nautical mile (both defined in meters), so the computed factor is exact based on those definitions. However, reported values are typically rounded and subject to measurement uncertainty when derived from instruments.

What precautions should I take for navigation or safety-critical use?

Use properly calibrated instruments, document measurement uncertainty, and follow relevant standards and operational procedures. Do not rely solely on an on-screen conversion for navigation; verify with certified instruments, official charts, and onboard systems.

Where do these unit definitions and best practices come from?

Unit definitions are set by international agreements and standards bodies; measurement and calibration practices are guided by national measurement institutes and consensus standards. See the citations for authoritative sources and accreditation guidance.

Sources & citations