Compare hp, bhp, PS and kW in car specifications

The short answer

hp, bhp, PS and kW all describe the same thing: power, meaning how quickly an engine or motor can do work. The kilowatt (kW) is the metric unit and the safest common basis for comparing cars. Horsepower comes in two main definitions. Mechanical horsepower (the US hp) equals 745.6999 watts. Metric horsepower, abbreviated PS from the German Pferdestärke, equals 735.4988 watts. One PS is therefore about 1.4% smaller than one mechanical hp, so the same engine shows a slightly bigger number in PS than in hp.

bhp, or brake horsepower, is a label rather than a separate unit size. On its own it does not tell you which horsepower definition or which test procedure was used. Before converting any figure, confirm which horsepower is meant and what was measured: the engine, the electric motor or the whole hybrid system.

What each abbreviation means

Label	What it is	Size in watts
kW (kilowatt)	Metric unit of power; 1 kW = 1,000 watts, and 1 watt = 1 joule per second	1,000 W
hp (mechanical horsepower)	Defined as 550 foot-pounds of work per second; the horsepower usually meant in US specifications	745.6999 W
PS (metric horsepower)	Also seen as DIN hp, CV or ch in some markets; confirm that metric horsepower is intended	735.4988 W
bhp (brake horsepower)	A power rating label; its unit definition and test basis must be confirmed from the source	Depends on the horsepower definition used

Is horsepower a unit of power?

Yes. Horsepower measures a rate of work: energy delivered per unit of time. It is not part of the International System of Units (SI). The SI unit of power is the watt, which is why kilowatts appear on European type-approval documents and on most electric-vehicle specifications.

Despite the name, one horsepower is not a count of horses. It is a fixed, defined quantity of 550 foot-pounds per second, or 745.7 watts for the mechanical version. The name is historical. The number tells you nothing about any real animal's output.

In a car, a quoted horsepower figure is a maximum output rating produced under a defined test. It is not the power the engine delivers at every moment of driving.

Conversion factors

kW = mechanical hp × 0.7456999
kW = PS (metric hp) × 0.7354988

mechanical hp = kW ÷ 0.7456999   (≈ kW × 1.341)
PS            = kW ÷ 0.7354988   (≈ kW × 1.360)

PS = mechanical hp × 1.0139
mechanical hp = PS × 0.9863

Converting between PS and hp only rescales the number. If a figure labelled bhp is really metric horsepower, applying the mechanical factor introduces an error of about 1.4%. Identify the definition first.

Quick reference: kW to hp and PS

kW	Mechanical hp	PS (metric hp)
50	67.1	68.0
75	100.6	102.0
100	134.1	136.0
150	201.2	203.9
200	268.2	271.9
300	402.3	407.9

Rating	Equals kW
100 hp	74.6
200 hp	149.1
300 hp	223.7
100 PS	73.5
200 PS	147.1
300 PS	220.6

In each row, every column describes the same amount of power. A 100 kW rating is about 134.1 hp, or about 136.0 PS if metric horsepower is confirmed. Neither figure is more powerful than the other.

Is PS the same as bhp?

Not necessarily. PS normally means metric horsepower. bhp is often used for mechanical horsepower, but the abbreviation alone does not guarantee that. When both appear for the same engine, the PS figure is typically about 1.4% higher.

Toyota's UK press release for the Aygo X Hybrid, dated September 23, 2025, shows this. It lists the petrol engine at 90 bhp, 91 DIN hp and 67 kW. It lists the electric motor at 79 bhp, 80 DIN hp and 59 kW. As an illustrative check, 67 kW converts to 89.9 mechanical hp and 91.1 metric hp, which matches the 90 bhp and 91 DIN hp figures after rounding. So in this release, Toyota's bhp behaves like mechanical horsepower and its DIN hp like PS. Treat that as specific to this document, not a universal rule.

Why a conversion is not always a fair comparison

Converting units fixes the arithmetic, not the test method. Two ratings are only comparable if they were measured the same way. For example, UN Regulation No. 85, the type-approval rule used in Europe, defines net power as power measured on a test bench at the end of the crankshaft (or equivalent). The engine must run with specified auxiliaries fitted and the result is corrected to reference conditions, including 25°C and 99 kPa dry air pressure. A rating taken under a different procedure can differ even after you put both figures in kW.

Wording such as hp, bhp or DIN hp in an advertisement does not by itself show which standard was used. For electric drivetrains, the same regulation defines maximum net power separately from maximum 30-minute power, so two EV figures in kW may describe different quantities.

Hybrids: engine, motor and system ratings

In a hybrid, the engine, the electric motor and the full system each have their own maximum rating. Toyota gives the Aygo X Hybrid system output as 114 bhp, 116 DIN hp and 85 kW. Adding the engine and motor figures (67 kW + 59 kW) gives 126 kW, which is not the stated system rating. Do not add component outputs together. Use the manufacturer's published system figure when comparing a hybrid with another car.

How to compare power figures across car listings

• Pin down the exact vehicle: model year, market and powertrain, since outputs often vary by market and version.
• Record the advertised number and its exact wording: hp, bhp, PS, DIN hp or kW.
• Confirm the unit definition: mechanical or metric horsepower. Do not assume that bhp means one or the other.
• Note the scope: engine only, electric motor only, or full hybrid system.
• Note the test basis where it is stated, such as a named net-power standard, and keep the source and its date.
• Convert everything to kW with the factors above, and compare only figures that share the same scope and rating basis.
• If one listing gives only a bare number with no unit or basis, treat it as unconfirmed until the manufacturer's specification for that exact version supports it.

Power output on its own does not predict acceleration, towing ability or how well a car suits a particular use. Weight, gearing, torque delivery and drivetrain all matter. Once you have two figures on a consistent kW basis, compare them alongside those other specifications, not instead of them.