Knots to Kph Converter

The Knots to Kph Converter translates speed between the nautical world and everyday road-and-weather units. The two main fields — Speed in knots and Speed in kph (km/h) — live together inside one bordered card so you can compare them at a glance. Open More conversion options to read the same speed in twelve additional units, from $\mathrm{m/s}$ and $\mathrm{mph}$ to $\mathrm{ft/min}$ and light speed.

Use it whenever a marine chart, aviation report, weather bulletin, or sailing log gives speed in knots but you want it on the km/h scale — or the reverse. The converter is a pure unit translation, so the result is the same physical speed written in a different unit, with no rounding or estimation added beyond ordinary display formatting.

All three fields share one internal base — meters per second. The calculator converts the authored field to $\mathrm{m/s}$ and then back out to each target unit. With $f_s$ the number of m/s in one source unit and $f_t$ the number of m/s in one target unit:

The two primary factors are exact definitions. A nautical mile is fixed at $1852\ \mathrm{m}$ and an hour is $3600\ \mathrm{s}$, so a knot is$\ 463/900\ \mathrm{m/s}$. A kilometer is $1000\ \mathrm{m}$, so a kilometer per hour is $5/18\ \mathrm{m/s}$. Dividing the two gives the familiar one-number factor:

Wider conversions through the “Speed in selected unit” row use the same idea. A foot is exactly $0.3048\ \mathrm{m}$ ($381/1250$), a yard $0.9144\ \mathrm{m}$, a statute mile $1609.344\ \mathrm{m}$, and the speed of light is the exact SI constant $299\,792\,458\ \mathrm{m/s}$. Every other unit in that dropdown is one of those length-over-time ratios, so every conversion is reversible and consistent: editing km/h re-derives knots and “selected unit,” editing “selected unit” re-derives the top two, and so on.