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Of HP, KW and PS

So, out of curiosity some time ago I looked at the UK website for a British car manufacturer. What I found interesting is they listed engine power output in Kilowatts (these were gas engines). I wondered how that would convert to horsepower, but didn’t have time to follow up at that time. So I had some extra time and found several websites that offer a conversion from KW to HP, but there are 3 different types of HP: mechanical, electric and metric. Really? Which to use? Then I checked a couple of British car websites and now they are listing power outputs in PS, which I’ve never in my whole life heard of. Uh, whiskey tango foxtrot, what is that? How does it convert? Of course there’s also the fact they list torque output in newton/meters instead of foot pounds, but now my head hurts. I could use a small amount of education here.

They all are about the same,± about 1%. 1 hp is about 0.75 KW. There are many more than two systems of units out there. Just last week I read they announced the survey foot would finally be phased out. Who knew?

I use the Converter + app, it has lots of options.


PS is a German acronym for horse power

newton/meters is a metric unit for torque

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“Metric HP” is just Killowatts. The conversion is 0.746 kW = 1 HP. A Newton is a measure of force, meter distance so 1 Newton-Meters is 0.738 Ft-lb.

Stranger is Kg-M to Ft-lb. 1 kg-Meters is 0.138 Kg-Meters

1 mechanical horsepower = 1 electric horsepower

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Thank you all for the information.

That just blew my mind! Most measurements are smaller and the difference is not significant… until it is. Precision is important… agreement in measurement is more important!

Ignore English measurements, use MKS!

The definition of gasoline engine HP has changed over the years. I think they used to use HP in the old days, now they use BHP. I’m not sure what the actual difference is, but it has to be kept in mind when comparing the specs for older cars vs newer cars.

Automobile starter motors are often spec’d in kw, for smaller engines usually a little over 1 kw.

The big change was in how it was measured. Used to be ‘gross hp’, with no accessories and through headers, then went to ‘net hp’, with accessories and actual exhaust system. BIG drop.


Not to mention that sometimes horsepower is measured at the flywheel and sometimes at the rear wheels, which will also be less due to losses in the power train.