CALTRX

MPH to Knots

Convert mph to knots. 1 mph = 0.868976 knots. For aviation and marine navigation.

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Knots

Tips & Notes

  • ✓Quick conversion: mph × 0.87 ≈ knots. Good for mental estimates (error: 0.1%).
  • ✓For flight planning: convert mph cruise speed to knots for ATC communications.
  • ✓Wind advisories in the US may use mph; METAR weather reports use knots internationally.
  • ✓Divide mph by 1.15078 as an alternative to multiplying by 0.868976 — same result.

Common Mistakes

  • ✗Forgetting that knots are always less than mph — 60 mph = 52.1 knots, not 69 knots.
  • ✗Using mph wind speeds in official NOTAM or METAR — these require knots.
  • ✗Confusing the direction — mph × 1.15 gives mph-equivalent knots (wrong); use × 0.869.
  • ✗Assuming road speed limits apply in knots — maritime and aviation speeds are in knots, not mph.

MPH to Knots Overview

What This Calculator Does

Converts miles per hour to knots: 1 mph = 0.868976 knots (= 1 ÷ 1.15078 exactly).

Sailing and Boating Reference

| mph | Knots | Sea Condition | |-----|-------|---------------| | 5.8 | 5 | Light wind, calm | | 11.5 | 10 | Slight chop | | 17.3 | 15 | Moderate waves | | 23.0 | 20 | Whitecaps forming | | 34.5 | 30 | Rough sea |

US Weather to Marine Conversion

US weather reports use mph; marine forecasts use knots. National Hurricane Center reports both. A 74 mph (Category 1 minimum) = 64.3 knots. VHF marine weather broadcasts use knots exclusively.

Aviation Note

FAA uses knots for airspeed. A Cessna 172 cruise of 122 mph = 106 knots. Air traffic control always uses knots — pilots must convert when reading US charts that show mph.

Frequently Asked Questions

60 × 0.868976 = 52.14 knots. This is a highway speed — fast for a ship, slow for an aircraft.

100 × 0.868976 = 86.9 knots. A fast speedboat or light aircraft approach speed.

550 × 0.868976 = 477.9 knots. This is roughly commercial jet cruise speed (typically 450-500 knots TAS).

Aviation worldwide uses knots for airspeed, wind, and navigation. Flight plans, ATC communications, and weather reports (METARs) all use knots. Even in the US, aviation switched to knots to align with ICAO international standards.