Velocity Unit Converter

Pipe velocity, vehicle speed and flow-meter ranges are quoted in m/s on one drawing, ft/s on a sensor and km/h or mph on a road, while marine and hydraulic work adds knots. This converter moves exactly between them with no approximation.

Convert velocity unit units

Value

From

Why velocity units collide

Velocity stacks a length unit on a time unit, so every length convention (metric, imperial, nautical) spawns its own speed: m/s and km/h, ft/s and mph, and the knot (nautical mile per hour). The conversions are all exact definitions — 1 km/h = 0.27778 m/s, 1 mph = 0.44704 m/s, 1 kn = 0.51444 m/s.

In piped flow the number that matters is the velocity through the bore, and mixing m/s with ft/s in a sizing calc is a direct error. Convert exactly, and keep the unit attached to the value.

Which unit where

m/s is the process and pipe-velocity standard; km/h and mph describe vehicles and site roads; ft/s appears on imperial flow and velocity probes; the knot belongs to marine, hydraulic and positioning work.

Complete conversion reference

Convert 1 unit to	m/s	km/h	ft/s	mph	kn
1 m/s	1	3.6	3.28084	2.23694	1.94384
1 km/h	0.277778	1	0.911344	0.621371	0.539957
1 ft/s	0.3048	1.09728	1	0.681818	0.592484
1 mph	0.44704	1.60934	1.46667	1	0.868976
1 kn	0.514444	1.852	1.68781	1.15078	1

Instruments for this measurement

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Lining PTFE/PU · DN10–1200

SV21

Vortex flowmeter, steam / gas / liquid

DN15–300 · no moving parts

SG61

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Direct mass & density

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Frequently asked

How do I convert m/s to km/h?

Multiply by 3.6: 1 m/s = 3.6 km/h. In the other direction 1 km/h = 0.27778 m/s. The converter applies the exact factor so you avoid the common decimal slip.

What is 1 mph in m/s?

Exactly 0.44704 m/s (1 mile = 1609.344 m, divided by 3600 s). One ft/s is 0.3048 m/s. These are defined, so the values are exact.

Why do pipe specs use m/s but probes use ft/s?

Metric process drawings quote bore velocity in m/s; imperial velocity probes and some US sensors report ft/s. Convert at the interface so a sizing or alarm threshold is not silently off by a factor.

What is a knot in m/s?

One knot is one nautical mile per hour, exactly 0.51444 m/s (1852 m / 3600 s). It is the marine and hydraulic speed unit and is not interchangeable with mph or km/h.

This page performs exact unit arithmetic with no physical assumption beyond the stated reference (for example mH₂O assumes water near 4 °C, and pH follows its logarithmic definition). It is a working aid, not a substitute for the measurement method named in your permit.