Miles per hour to kilometers per hour converter

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

Direct example

1 mph ≈ 1.609344 km/h.

Formula and calculation

km/h = mph × 1.609344

Substituting 1 mph gives approximately 1.609344 km/h. 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?

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

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

When this direction is useful

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

Conversion table

Approximate displayed values, with the same definitions as the converter
miles per hour (mph)	kilometers per hour (km/h)
0	0
1	1.609344
5	8.04672
10	16.09344
100	160.9344

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 kilometers per hour to miles 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.