Watts Per Kg Calculator

Welcome to Calculator Value. Have you ever wondered what it actually means when someone says “I ride at 4 W/kg”? Don’t worry, we explain what it means, how it works, and more.

If you are a runner, cyclist, rower, or someone who wants to measure performance based on power and weight, then you are in the right place. We have prepared a Watts per kg calculator that uses your power and weight to calculate your W/kg.

What is Watts per kg?

Watts per kilogram (W/kg) is a common performance metric in sports. It shows how much power you can generate per kilogram of your body weight. In simple terms, it shows how strong you are relative to your body weight. See the following simple logic:

• Higher W/kg means a better power-to-weight ratio
• Lower W/kg means more weight relative to your power

In sports like running, rowing, and cycling, athletes use it a lot because your weight directly affects your performance, especially when gravity is involved.

You might be curious how exactly it is calculated. Keep reading to learn more.

How is Watts per kg Calculated?

The equation behind the calculator is much simpler than you might think. You can divide your power in watts by your weight in kg to get the watts per kg (W/kg) ratio.

Here is the equation:

W/kg = Power (W) / Weight (kg)

For instance, if your power output is 250 watts and your weight is 70 kg, then your power-to-weight ratio is 3.57 W/kg.

If you need unit conversion between kilogram and pound:

1 lb = 0.45359237 kg

Real-World Example

Let’s apply it to a real-world scenario to understand it better with a simple two-step calculation, and we'll use a cyclist doing a hard climb as an example.

Suppose you climbed a steep mountain on your bike with high effort. To calculate, determine your power output e.g. 300 watts, and your weight e.g. 65 kg.

How Watts per kg works in different sports

Here we explain how cyclists, rowers, and runners use W/kg in their sport, and we provide typical W/kg ranges.

Watts per kg Calculator – Cycling

Watts per kg is very common in cycling, to calculate it you need your Functional Threshold Power (FTP) which is essentially your sustained power output. FTP means the highest power you can sustain for a long time and it is commonly measured from a 20-minute maximum effort test.

You might be wondering how to measure FTP in cycling. Typically there are two methods to measure your FTP, which are Formal FTP Test and Power Curve.

• Formal FTP Test: 20-minute FTP Test is considered one of the most common methods. To test, you have to ride your bike with maximum sustainable effort for 20 minutes. Then, to calculate your FTP, multiply the average power from the test by 0.95.
• Determining via a Power Curve: Training platforms can estimate your FTP from your historical high-intensity efforts and your ride data.

For instance, if your Functional Threshold Power (FTP) is 280 watts and your body weight is 70 kg, let's compute:

W/kg = 280 W / 70 kg = 4.0 W/kg

Here is the general W/kg ranges based on experience:

Watts per kg Calculator – Rowing

In rowing, watts per kg can be generally calculated on an indoor rowing machine and the same W/kg formula works for it. For lightweight rowers, W/kg works well. For heavier rowers who generate more absolute power, coaches often prioritize total power instead of W/kg.

High-performance power can be calculated from a 2,000-meter (2K) ergometer test on an indoor rowing machine, while most modern ergometers show watts and pace (time per 500 m).

The power can be calculated from two metrics watts and pace:

$$$ \text{Watts}=\frac{2.80}{{\text{(Pace in seconds/500m)}}^3}$$$

Example:

For instance, If your average 500m split time for a 2K is 1:40 (100 seconds), let's compute your average power:

$$$ \text{Watts}=\frac{2.80}{(100/500{)}^3}=\frac{2.80}{(0.20{)}^3}=\frac{2.80}{0.008}=350\text{ Watts}$$$

Now divide that power 350 watts by your weight e.g. 75 kg:

• Average Power: 350 Watts
• Body Weight: 75 kg

W/kg = 350 W / 75 kg = 4.6

Now see the following typical W/kg reference on a 2k rowing:

Watts per kg Calculator – Running

In running, estimating the watts per kg is more complicated than in rowing and cycling, because determining power is a tough task in running.

While the W/kg formula is the same:

W/kg = Average Running Power (watts) / Weight (kg)

Average Running Power shows the energy you use to move your body forward and upward against gravity. Determining power in running is complex because it accounts for factors such as horizontal power, vertical power and elevation power.

Thinking how exactly the average running power is estimated? The GPS and pace are not enough to estimate the power, while there are two ways to calculate power:

• Running Power Meters: Specialized sensors worn on your foot, waist, or chest that use accelerometers and barometers to estimate the power you are using.
• High-end smartwatches: There are some new advanced smartwatches that have built-in features to determine your power while running, but the external power meters are more accurate and reliable.

For instance, you run with high effort and your average running power is 260 watts, and your weight is 80 kg.

• Average Running Power: 260 Watts
• Weight: 80 kg

W/kg = 260 W / 80 kg = 3.25

For reference, look at the following running W/kg: