# Definitions of HORSEPOWER and ENGINE DISPLACEMENT

When talking about cars many people are often confused about what the words “horsepower” and “engine displacement” mean. That’s why today we are going to explain these two technical terms, which are actually simpler than you think.

HORSEPOWER (hp) is a unit of measurement of power (the rate at which work is done). In other words it’s the common measurement of an engine’s output. By pure definition, one horsepower is the power needed to lift 550 pounds one foot off the ground in exactly one second. There are many different standards and types of horsepower. The most common horsepower is 1 hp = 746 watts. This means that to convert from horsepower to watts, we have to multiply by 746. To convert from watts to horsepower, we will multiply by 0.00134. There’s no magic number for ideal horsepower, as other variables like vehicle weight, aerodynamics, and gearing all play supporting roles in the car’s overall performance.

ENGINE DISPLACEMENT is a measure of the volume in an internal combustion engine. Though not directly proportional to total power produced, it typically correlates strongly with output power. As cylinders move within an engine, they do work by displacing a certain volume of air. All internal combustion engines have a certain volume displaced by cylinders. In other words, it’s the volume swept by all the pistons inside the cylinders of a reciprocating engine in a single movement from top dead centre (TDC) to bottom dead centre (BDC). It is commonly specified in cubic centimetres (cc or cm3), litres (l), or (mainly in North America) cubic inches (CID). Engine displacement does not include the total volume of the combustion chamber. Resources: