Speed Converter
Convert speed between meters per second, kilometers per hour, miles per hour, knots and feet per second using exact factors, with a worked example.
Results
Result
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Educational estimates · not financial advice · free, no signup
Formula / how it works
Converts through m/s. 1 km/h = 0.277778 m/s; 1 mph = 0.44704 m/s (exact); 1 knot = 0.514444 m/s (1 nautical mile per hour); 1 ft/s = 0.3048 m/s.
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Speed is reported in different units depending on where you are and what is moving. Road signs use km/h or mph, aviation and shipping use knots, physics uses metres per second and some engineering uses feet per second. This converter changes a value between any pair of these. Drivers use it when travelling abroad, pilots and sailors for navigation figures, and students for physics work. The conversions use the defined relationships: a mile is exactly 1,609.344 m and a knot is one nautical mile (1,852 m) per hour.
When to use / who it helps
- You are driving abroad and want to relate unfamiliar speed limits to ones you know.
- You are reading a weather report giving wind in knots and want km/h or mph.
- You are solving a physics problem needing m/s.
- You want to compare a runner's pace with a vehicle's speed.
- You are checking aviation or marine speed figures.
How to use
Steps
- Enter the value to convert.
- Select the starting unit in From.
- Select the target unit in To.
- Read the converted value.
- Swap the units to confirm the round trip.
- Use rounding that suits the context; road speeds need whole numbers.
How to interpret results
- 100 km/h is about 62.1 mph, so a 50 mph limit is about 80 km/h.
- One knot is about 1.852 km/h or 1.151 mph.
- Metres per second multiplied by 3.6 gives km/h.
- The result is a unit conversion, not a prediction of travel time.
- Keep extra digits for intermediate steps and round only at the end.
Common mistakes & gotchas
- Confusing knots with km/h; a knot is 1.852 km/h.
- Using 1.6 as the km per mile factor in a precise calculation; the exact value is 1.609344.
- Dividing instead of multiplying when converting from m/s to km/h.
- Assuming speed limits in different countries use the same unit.
- Rounding to whole numbers before multiplying by time.
Worked example
Worked example — 100 km/h in other units
- To m/s: 100 ÷ 3.6 ≈ 27.78 m/s.
- To mph: 100 ÷ 1.609344 ≈ 62.14 mph.
- To knots: 100 ÷ 1.852 ≈ 53.99 knots.
- To ft/s: 27.78 ÷ 0.3048 ≈ 91.13 ft/s.
Result: 100 km/h is about 27.8 m/s, 62.1 mph, 54.0 knots or 91.1 ft/s.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
Converts through m/s. 1 km/h = 0.277778 m/s; 1 mph = 0.44704 m/s (exact); 1 knot = 0.514444 m/s (1 nautical mile per hour); 1 ft/s = 0.3048 m/s.
Frequently asked questions
How do I convert km/h to mph?
Divide by 1.609344. As a quick check, multiply by 0.62.
What is a knot?
One nautical mile per hour, equal to exactly 1.852 km/h.
How do I convert m/s to km/h?
Multiply by 3.6.
Why do pilots and sailors use knots?
A nautical mile corresponds to one minute of latitude, which makes navigation calculations easier.
Are these factors exact?
The mile, foot and nautical mile are defined exactly in metres, so the conversions are exact up to rounding.
Can I convert pace such as min/km?
Not here. Use a pace helper, which converts minutes per kilometre to speed.