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Convert miles per hour to knots instantly with our free online calculator. Essential for maritime navigation, aviation flight planning, weather reporting, and international speed communication.
0.868976
Knots per mph
1.15078
mph per Knot
1,852 m
Meters per Nautical Mile
Formula: Knots = mph × 0.868976
| MPH | Knots | Context |
|---|---|---|
| 5 mph | 4.34 kn | Slow sailboat cruising speed |
| 10 mph | 8.69 kn | Average rowing shell speed |
| 20 mph | 17.38 kn | Small powerboat speed |
| 30 mph | 26.07 kn | Recreational sailing boat |
| 50 mph | 43.45 kn | Fast powerboat / small aircraft |
| 60 mph | 52.14 kn | Cruising speedboat |
| 75 mph | 65.17 kn | Racing speedboat |
| 100 mph | 86.90 kn | Light aircraft cruising speed |
| 150 mph | 130.35 kn | Small turboprop aircraft |
| 200 mph | 173.80 kn | Twin-engine aircraft |
| 250 mph | 217.24 kn | Fast single-engine aircraft |
| 300 mph | 260.69 kn | Business jet |
| 400 mph | 347.59 kn | Regional jet |
| 500 mph | 434.49 kn | Commercial jetliner cruise |
| 575 mph | 499.66 kn | Boeing 737 typical cruise |
Miles per hour (mph) is a unit of speed used primarily in the United States and the United Kingdom for road vehicles and general terrestrial speed measurement. One mph is defined as traveling one statute mile (5,280 feet or 1,609.344 meters) in one hour. This measurement system originates from the imperial system and has been the standard for automobile speedometers and highway speed limits in the US since the early 20th century.
A knot (symbol: kn or kt) is a unit of speed equal to one nautical mile per hour. One nautical mile is defined as exactly 1,852 meters (6,076.12 feet), which is approximately one minute of arc of latitude along any meridian. The term "knot" comes from the historical maritime practice of measuring a ship's speed using a "common log" — a rope with knots tied at regular intervals. Sailors would throw the log overboard and count how many knots passed through their hands in a specific time period, typically measured with a sandglass.
The relationship between these units is: 1 mph = 0.868976 knots, or conversely, 1 knot = 1.15078 mph. Knots are the international standard for maritime and aviation speed worldwide because nautical miles relate directly to Earth's coordinate system, making navigation calculations significantly simpler. Every 60 nautical miles traveled north or south equals exactly one degree of latitude change, regardless of your position on Earth.
The formula to convert miles per hour to knots is: Knots = mph × 0.868976. Simply multiply the mph value by the conversion factor 0.868976 to get the equivalent speed in knots.
Question: A sailboat is traveling at 20 mph. What is this speed in knots?
This is a typical cruising speed for a small recreational sailboat in moderate wind conditions.
Question: A Cessna 172 cruises at 120 mph. Convert to knots for a flight plan.
Aviation charts, air traffic control, and flight computers all use knots as the standard airspeed unit.
Question: A Boeing 737 cruises at 550 mph. What is this in knots?
For a quick estimate, multiply mph by 0.87 (slightly higher than the exact factor of 0.868976, but easier to calculate mentally). This gives you accuracy within 0.15%. For example: 100 mph × 0.87 = 87 knots (exact: 86.90). Another useful trick: subtract about 13% from the mph value. So 100 mph − 13 = 87 knots. Both methods work well for quick approximations when precise calculations aren't critical.
| Vessel Type | MPH | Knots |
|---|---|---|
| Kayak (paddling) | 3–5 | 2.6–4.3 |
| Rowing shell | 10–12 | 8.7–10.4 |
| Sailboat (cruising) | 15–25 | 13.0–21.7 |
| Fishing trawler | 12–18 | 10.4–15.6 |
| Cargo ship | 15–25 | 13.0–21.7 |
| Ferry (passenger) | 25–35 | 21.7–30.4 |
| Container ship | 20–25 | 17.4–21.7 |
| Cruise ship | 20–24 | 17.4–20.9 |
| Destroyer (naval) | 35–40 | 30.4–34.7 |
| Racing yacht | 30–50 | 26.1–43.4 |
| Speedboat | 50–80 | 43.4–69.5 |
| Hydrofoil ferry | 40–60 | 34.7–52.1 |
| Aircraft Type | MPH | Knots |
|---|---|---|
| Ultralight / hang glider | 20–35 | 17.4–30.4 |
| Hot air balloon | 5–15 | 4.3–13.0 |
| Cessna 172 (trainer) | 110–130 | 95.6–113.0 |
| Piper Cherokee | 120–140 | 104.3–121.7 |
| Cirrus SR22 | 180–210 | 156.4–182.5 |
| King Air 350 (turboprop) | 310–360 | 269.4–312.8 |
| Beechjet 400 | 460–520 | 399.7–451.7 |
| Learjet 75 | 480–535 | 417.1–465.0 |
| Boeing 737 | 500–550 | 434.5–477.9 |
| Airbus A320 | 510–560 | 443.2–486.6 |
| Boeing 777 | 560–590 | 486.6–512.5 |
| Gulfstream G650 | 610–680 | 530.1–590.7 |
| Wind Condition | MPH | Knots |
|---|---|---|
| Light breeze | 4–7 | 3.5–6.1 |
| Gentle breeze | 8–12 | 7.0–10.4 |
| Moderate breeze | 13–18 | 11.3–15.6 |
| Fresh breeze | 19–24 | 16.5–20.9 |
| Strong breeze | 25–31 | 21.7–26.9 |
| Near gale | 32–38 | 27.8–33.0 |
| Gale | 39–46 | 33.9–40.0 |
| Strong gale | 47–54 | 40.8–46.9 |
| Storm | 55–63 | 47.8–54.7 |
| Violent storm | 64–72 | 55.6–62.5 |
| Hurricane (Cat 1) | 74–95 | 64.3–82.5 |
| Hurricane (Cat 5) | 157+ | 136.4+ |
All aircraft worldwide report airspeed, groundspeed, and wind speed in knots. Air traffic control communications, flight planning, weather briefings, and aircraft performance charts exclusively use knots. Understanding mph-to-knots conversion is essential for student pilots, flight dispatchers, and anyone involved in aviation operations.
Ships, boats, and all nautical charts use knots for speed measurement. Maritime weather forecasts report wind and current speeds in knots. Understanding this conversion helps recreational boaters, professional mariners, and yacht racers communicate effectively and plan passages accurately using international standards.
Aviation weather reports (METARs and TAFs) express wind speeds in knots, while US public weather forecasts typically use mph. Meteorologists, emergency managers, and weather enthusiasts need conversion fluency to interpret international weather data and tropical cyclone advisories accurately.
The International Civil Aviation Organization (ICAO) and International Maritime Organization (IMO) mandate knots for all official documentation. Commercial operators, search and rescue coordination, and international regulations all rely on knots, making conversion knowledge essential for professional compliance and safety.
Multiplying mph by 0.87 is easier than 0.868976 and gives results within 0.15% accuracy — perfectly acceptable for most practical purposes.
Since 1 knot = 1.15 mph, your knots result should always be smaller than your mph input. If knots is bigger, you've converted the wrong direction.
Aviation typically uses whole numbers or one decimal (e.g., 87 knots or 86.9 knots). Maritime navigation may use two decimals for precision plotting.
A nautical mile (6,076 ft) is about 15% longer than a statute mile (5,280 ft). Using the wrong mile type leads to significant navigation errors over long distances.
MPH to knots requires multiplication by 0.868976. Dividing by 0.868976 converts knots to mph — the opposite direction. Double-check your formula.
While close, this approximation has a 15% error. For aviation and maritime use, even small speed errors can lead to fuel miscalculations and arrival time mistakes.
One mile per hour equals exactly 0.868976 knots. This means 1 mph is about 87% of a knot. To convert any mph value to knots, multiply by 0.868976. For example, 100 mph equals 86.8976 knots.
Knots are faster. One knot equals approximately 1.15078 mph. So a knot is about 15% faster than a mile per hour. A knot is one nautical mile per hour (1,852 meters/hour), while mph is one statute mile per hour (1,609.34 meters/hour).
Multiply the mph value by 0.868976. For example: 50 mph × 0.868976 = 43.45 knots. For a quick mental estimate, multiply mph by 0.87, which gives you accuracy within 0.1%.
Knots are based on nautical miles, which correspond directly to latitude and longitude on charts. One nautical mile equals one minute of latitude, making navigation calculations much simpler. This standardization is essential for international maritime and aviation safety.
A nautical mile is 6,076 feet (1,852 meters), while a statute mile (regular mile) is 5,280 feet (1,609.34 meters). A nautical mile is about 15% longer. Nautical miles are used in maritime and air navigation because they relate directly to Earth's coordinate system.
100 mph equals approximately 86.90 knots. This is calculated as 100 × 0.868976 = 86.8976, rounded to 86.90 knots. This speed is typical for small general aviation aircraft.
Yes. The conversion is based on the exact definitions: 1 nautical mile = 1,852 meters and 1 statute mile = 1,609.344 meters. Therefore, 1 mph = 1,609.344/1,852 knots = 0.86897624190065... knots. The factor 0.868976 is rounded to six decimal places, which is precise enough for virtually all practical navigation purposes.
All commercial and general aviation aircraft worldwide use knots for airspeed. Air traffic control, flight plans, weather reports, and aircraft instruments display speeds in knots. This international standard ensures consistent communication and safety across all airspace.
One knot equals approximately 1.15078 mph. This is the inverse of the mph-to-knots conversion. To convert knots to mph, multiply by 1.15078. For example, 50 knots × 1.15078 = 57.54 mph.
This calculator uses the internationally recognized conversion factor based on the exact definitions of statute miles (1,609.344 meters) and nautical miles (1,852 meters). For official flight planning, navigation, and maritime operations, always verify speeds with certified instruments and consult current aviation/maritime regulations and charts.