How to read car specifications
Car spec sheets are full of numbers, but a few of them tell you most of what you need to know. This guide explains the key technical figures you will find on our model pages and rankings, and what they really mean.
Power: kW and horsepower
Engine power is given in kilowatts (kW); we also show horsepower (hp) in brackets, where 1 kW is roughly 1.34 hp. More power means stronger acceleration and a higher top speed, but weight and gearing matter too.
You can see which models top the charts on our most powerful cars and fastest cars rankings.
Top speed
Top speed is the maximum rated speed of the car, taken from type-approval data. It is more of a headline figure than a practical one, but it is a useful way to compare high-performance models. See the fastest cars ranking for the full list.
Dimensions and weight
Length, width and height define how big a car is and how it fits in a garage or parking space; length is the figure used in our largest cars ranking. Kerb weight affects acceleration, braking and efficiency.
CO2 and fuel economy
CO2 emissions are measured in grams per kilometre under the WLTP standard; lower is cleaner, and it is the figure used in our lowest-CO2 ranking. Fuel economy (litres per 100 km, or miles per gallon) tells you running cost. Note that test standards differ: Europe uses WLTP, while US EPA figures are measured differently and are not directly comparable.
Electric cars emit no CO2 at the tailpipe, so they are excluded from the CO2 ranking.
See the data
Frequently asked questions
- How many horsepower is 100 kW?
- About 134 hp. One kilowatt is roughly 1.34 horsepower.
- What is WLTP?
- WLTP is the European test standard for fuel consumption and CO2 emissions. It is more realistic than the older NEDC standard, and it is the figure used for European taxation.
- Are EPA and WLTP figures comparable?
- Not directly. They use different test cycles, so a car will show different numbers under each. We label which standard a figure comes from.