Enter a speed in km/h to find its equivalent speed in miles per hour.
This is the same speed in a different unit. It is not a pace conversion or a new legal speed limit.
Table of contents
How to use our KMH to MPH Converter
- Enter the source speed in "Speed in kilometers per hour (km/h)." A number by itself means km/h, or you can add km/h, kph, or kmh.
- Open "Advanced options" if you want to change "Result decimal places." This changes displayed rounding only.
- Select "Calculate" to see "Speed in miles per hour (mph)."
- Sanity-check the result: 100 km/h is about 62.14 mph when "Result decimal places" is set to 2.
Definitions
km/h: Kilometers per hour, a speed unit that tells how many kilometers are traveled in one hour.
mph: Miles per hour, a speed unit that tells how many miles are traveled in one hour.
International mile: A mile equal to exactly 1,609.344 meters, or 1.609344 kilometers.
Decimal places: The digits shown after a decimal point. This setting changes displayed rounding, not the conversion value.
Common mistakes and quick fixes
Mistake: Entering a speed already stated in mph.
Fix: This page converts from km/h to mph only. Enter the source value stated in km/h, kph, or kmh.
Mistake: Typing a pace such as 5 min/km.
Fix: Minutes per kilometer is pace, not speed. Use a pace converter for that kind of value.
Mistake: Using a comma as a decimal mark, such as 1,5.
Fix: Use a decimal point for fractions, such as 1.5. Commas are only for thousands grouping, such as 1,000.
Mistake: Rounding the km/h value before converting it.
Fix: Enter the most precise source value available, then choose the decimal places for the mph display.
Mistake: Treating the converted value as a new road-speed rule.
Fix: The result is the same speed in another unit. Follow posted limits and local road rules.
Limitations & Key Assumptions / Boundary Conditions
- The calculator converts a nonnegative speed only. It does not calculate travel time, distance, pace, acceleration, or direction.
- Negative entries are rejected because speed has no direction and cannot be negative. A signed quantity with direction is velocity.
- The displayed mph value can be rounded. Choose more decimal places when comparing specifications or completing schoolwork.
- A converted road-sign value is a unit equivalent, not a legal speed limit or a safe-speed recommendation.
- The source field accepts km/h, kph, and kmh suffixes, but not mph because the conversion direction is fixed.
Methodology
Conversion method
The time unit stays the same, so the calculation converts only the distance unit. One international mile equals exactly 1.609344 kilometers.
speed_mph = speed_kmh / 1.609344
mph_per_kmh = 1 / 1.609344 = approximately 0.621371192237334
Worked example
For 100 km/h, divide 100 by 1.609344. The unrounded value is approximately 62.137119 mph, so it displays as 62.14 mph with two decimal places.
100 km/h / 1.609344 = 62.137119... mph
Rounding
The calculator uses the unrounded converted value and rounds only the visible mph result to your selected decimal places. Zero is valid: 0 km/h converts to exactly 0 mph.