Power-to-Weight Ratio Calculator
Engineers will find our power-to-weight ratio calculator a handy tool to measure the performance of an engine.
In this article, you will learn:
- What is the power-to-weight ratio?
- How to calculate the power-to-weight ratio?
- How does the power-to-weight ratio affect the performance of a vehicle?
What is the power-to-weight ratio?
The power-to-weight ratio is a vehicle specification which somehow uniforms the comparison of the performance of a vehicle-engine pair.
The ability of an engine to supply a vehicle with acceleration and speed is measured in power. The power of an engine is assimilable to the energy output per unit of time: we can measure it in watts or, traditionally, in horsepowers.
The power, however, is not everything. Put the engine of a Dodge Viper on a Reliant Robin, and you will easily understand why!
How do I calculate the power-to-weight ratio formula?
To calculate the power-to-weight ratio, be sure to know:
- The weight of the vehicle ; and
- The power of the engine .
The formula for the power-to-weight ratio is simple:
As you can see, the weight of the vehicle is at the denominator: the heavier the vehicle, the lower the power-to-weight ratio. The same effect comes from a lower power.
A lower gives the platform worse performances. If you want a car that accelerates quickly and goes fast, check for higher values of power-to-weight ratio.
🙋 You can calculate the power-to-weight ratio also using the engine's weight, though this will not give you all the information about the vehicle's performance.
Not only cars: how to measure the power-to-weight ratio in different situations
The power-to-weight ratio is not exclusive to cars or motorcycles. Since moving from one place to another requires performing work (in the physical sense) — that is energy — in a given time, we can define a power.
You have a power-to-weight ratio. It doesn't really matter when you are walking in the city, but the moment you don a backpack and head for the mountain, it does matter! That's why you want to pack light. The same holds for running: look at how lean is a marathon runner compared to a sprinter.
We can apply the power-to-weight ratio to cycling, too: it's even easier to calculate: To measure the power-to-weight ratio of a cyclist, you only need aand a scale!
Planes, rockets, and helicopters all have a power-to-weight ratio, though it's common to express the performance of flying vehicles using the lift-to-drag ratio or the thrust-to-weight ratio.
Examples of power-to-weight ratio calculations in real life
Now that you know how to calculate the power-to-weight ratio let's see some examples where we can apply the formula for the power-to-weight ratio.
- A DeLorean DMC-12 (the car of Back to the Future), has a weight of (or ), and a power output of (), which gives it a power-to-weight ratio of .
- The two engines of a Boeing 777, the GE 90-115B supply a power of (). The maximum weight of the plane is or . The power-to-weight ratio we calculate is... : The same as the DeLorean!
- A cyclist in a really good shape can produce easily of power. The power-to-weight ratio is . Lance Armstrong, by comparison, is assumed to have produced more than at his peak performance. Look at the difference between planes and cyclists, but remember: two wheels and pedals are the best way to move!