Kilometers per hour to miles per hour converter

Read a quantity in km/h, then express the same speed in mph. The units are defined below to avoid mixing similarly named standards.

Direct example

1 km/h ≈ 0.621371192237 mph.

Formula and calculation

mph = km/h × 0.621371192237

Substituting 1 km/h gives approximately 0.621371192237 mph. Definitions use the constants above; arithmetic uses browser floating point and displays at most 12 significant digits. The rounded table is not an instrument calibration or certified measurement.

Which units does this page use?

kilometers per hour: speed of one kilometre travelled per hour.

miles per hour: speed of one international mile travelled per hour.

When this direction is useful

Start here when your source record uses km/h for speed limits and vehicle speed displays, but the receiving specification is expressed in mph for vehicle speed displays and international travel. Enter the original quantity rather than reusing a previously rounded result. If your source uses mph, use the reverse converter instead.

Conversion table

Approximate displayed values, with the same definitions as the converter
kilometers per hour (km/h)	miles per hour (mph)
0	0
1	0.621371192237
5	3.10685596119
10	6.21371192237
100	62.1371192237

Limits and interpretation

These are non-negative physical quantities; negative inputs are rejected. Converting a unit changes neither the measured object nor the original precision. Use a decimal dot; grouping commas are not accepted. No external rates, live data or account are involved.

Frequently asked questions

Can I convert the other way?

Yes. Convert miles per hour to kilometers per hour with the inverse equation. Rounding a result before converting it back can introduce a small difference.

Are these the same as every similarly named unit?

No. Check the two definitions above. International length, avoirdupois mass, US customary liquid measures and temperature readings are explicitly distinguished; an ambiguous label on a source document must be resolved first.

Where do the conversion definitions come from?

They use SI and defined customary conversion relationships. See the NIST Guide for the Use of SI. Output formatting is this tool's display policy, not extra measurement accuracy.