Miles per Hour to Meters per Second Converter | mph to m/s

What this converter does

You read speeds in miles per hour, but physics works in metres per second, so an mph figure has to be converted before it can go into a calculation. This converter takes a speed in mph and gives you m/s. Enter the mph value and you have the number a formula can use.

The factor, and why it is exact

One mile per hour is 0.44704 metres per second, so:

m/s = mph × 0.44704

That figure is exact rather than rounded, which is worth knowing. A mile is defined as exactly 1,609.344 metres, and an hour is 3,600 seconds, so dividing one by the other gives 0.44704 with nothing trailing off. The m/s value always comes out smaller than the mph, a little under half, because a metre per second is a much larger unit of speed.

A quick estimate

The factor is close to 0.447, so for a fast figure, a little under half the mph value gets you there. Take 60 mph, half is 30, ease it down and you are near 27, and the exact answer is 26.8 m/s. Halving and trimming a touch is an easy way to bring an mph speed into m/s when you just need a rough sense of it.

A worked example

Say a car is doing 60 mph and you need that in m/s for a physics problem, perhaps a stopping distance or an impact energy.

• 60 × 0.44704 = 26.8 m/s

So 60 mph is about 26.8 m/s. That is the number the formula needs, and it hints at why a crash at highway speed is so violent: energy rises with the square of that 26.8, so the speed packs far more punch than its modest mph label suggests.

Common mph speeds in m/s

As anchors, a 30 mph town limit is about 13.4 m/s, and 70 mph works out near 31.3 m/s.

When you need it

This is the direction for taking a road-world speed into physics. Students convert mph to m/s as the first step in a problem, so the rest of the working stays in SI units. Engineers and accident investigators do the same when a vehicle speed has to enter calculations of energy, braking, or force. It also helps when comparing an mph figure against scientific data that is published in m/s, since both need to be in the same unit first. Any time an mph speed is the input to a calculation, this is the conversion that prepares it.

Questions people ask

How do I convert mph to m/s?

Multiply the speed in mph by 0.44704. The factor is exact, so the result is precise. For a quick estimate, take a little under half the mph figure.

Is the conversion exact?

Yes. A mile is defined as exactly 1,609.344 metres and an hour is 3,600 seconds, so one mph is exactly 0.44704 m/s.

What is 60 mph in m/s?

About 26.82 m/s. It is a useful anchor, since 60 mph is a common highway speed.

References

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (unit conversion factors). https://www.nist.gov/pml/special-publication-811
2. International Bureau of Weights and Measures (BIPM), The International System of Units (SI) Brochure (metre per second as the SI unit of speed). https://www.bipm.org/en/publications/si-brochure