Watts Per Kg For Cyclists Explained (With W/kg Calculator)

It might not fit our romantic ideal of cycling, of man against machine and mountain, but it is an undeniable truth that numbers win bike races.

And no number is more sacred, more enshrined in cycling folklore, than the power-to-weight ratio. 

Typically measured in Watts per kg (W/kg), it is a measure of the power a cyclist can generate relative to their body weight. The higher the number, the more efficient the cyclist. 

In this article, we will investigate this hallowed number in more detail to find out why it gives the pros sleepless nights on training camps and how we can improve our power-to-weight ratio.

We’ll be covering:

• Why Is Watts Per Kg An Important Metric For Cyclists?
• What Is A Good Watts per Kg Ratio?
• How Can You Measure Your Watts/Kg?
• The BikeTips W/kg Calculator
• How Can You Improve Your Watts Per Kg?

Let’s dive in!

Why Is Watts Per Kg An Important Metric For Cyclists?

Despite the recent trend to more frequent and longer time trials in the Grand Tours, it’s not a vast exaggeration to claim that the races are won on power-to-weight ratios above all else. 

Obviously, this is an oversimplification, especially in the chaotic world of stage racing, but it is probably still true that you can’t win without a strong W/kg ratio. 

If you spend most of your time on flattish terrain, then it is probably fair to say that raw power (and how well you can sustain it) is more important than your power-to-weight ratio.

This is why we see the bigger guys come to the front of the peloton on those flat sprint stages whilst the climbers hide in the pack.

But once the race turns to the sky in the high mountains, dreams of winning live or die by the W/kg ratio.

Given that the Grand Tours are typically won and lost in the mountains, this makes the Watts per kilogram ratio decisive in determining champions.

Whilst Watts per kg has been used by the pros for years in the pursuit of marginal gains, it is increasingly becoming part of the lexicon for the average rider – and for good reason. 

More than anything, it is a great indicator to keep a track of a cyclist’s general condition over time. A high Watts per kg ratio suggests a strong lean muscle mass proportion and an overall stronger aerobic capacity.

What Is A Good Watts per Kg Ratio?

It is close to being a mantra that you need 6 W/kg to have any chance of wearing the yellow jersey by the time Le Tour trundles down the Champs-Élysées.

This means being able to generate 6 Watts of power for every kilogram of body weight, sustained for an hour. This is the number that keeps pros awake at night.

A decent amateur rider can likely hold 3 W/kg for an hour.

At the other end of the spectrum, a recreational rider, someone that likes the odd spin at the weekend, may have a power-to-weight ratio of around 1.8 W/kg.

Whilst there are lots of factors that separate the professionals from the best club riders, it is perhaps most obvious in the W/kg. Even if both riders were the same weight, the pro is likely putting out more than double the power, allowing them to climb significantly faster.

How Can You Measure Your Watts/Kg?

Time for some simple math.

If you want to find out your own power-to-weight ratio you only need to measure two things; your power and your weight. So far, so obvious.

If you don’t know your weight, then it is time to face your fear, wipe the dust from the bathroom scales, and find out. 

The other part of the equation, the power, is harder to measure and usually requires access to a power meter.

A power meter used to be the preserve of the pro-peloton but thanks to the magic of trickle-down technology, more and more amateur cyclists are using them as part of their day-to-day training.

The recent boom in indoor training thanks largely to virtual rides on Zwift means that many riders now have dedicated indoor bikes that directly measure power. 

Before testing your power, make sure you are properly warmed up. Then, simply ride as hard as you can for 20 minutes and note your average power across that time.

Your W/kg over one hour will be between 5 and 10 percent lower than your 20-minute effort, depending on your overall fitness.

If you don’t have access to a power meter (and it must be said they are still not cheap) you can estimate your average power, but it is going to involve a lot more math and even more assumptions. 

The BikeTips W/kg Calculator

How Can You Improve Your Watts Per Kg?

On a fundamental level, there are two ways that you can improve your W/kg; reducing your body weight or increasing your power.

Ideally, you should work on both. 

No matter how you approach the problem, it is important to remember that changing one will likely adversely affect the other. 

Shed weight too fast and without a proper plan, and you will quickly lose the power. The muscle mass increase that comes with increasing power will see your weight increase.

It is therefore a delicate balancing act to find the optimal W/kg for your body composition and your type of riding.

How you should approach improving your W/kg will also depend on your cycling experience. 

Watts per Kg for Beginners

When you are just starting out on the bike, perhaps after a long absence where the business of life was in the way, just getting in regular miles will raise your power-to-weight ratio.

It is a two-fold process; your aerobic fitness will improve, and you will start to cast off excess weight.

Both of these will work together to exponentially improve your W/kg when you are just starting out. When you have just been bitten by the cycling bug, it doesn’t even feel like exercise. 

Watts per Kg for Experienced Riders

Experienced riders will know that even making small improvements in performance means training smarter.

Just getting in miles will no longer cut it, except for the obvious enjoyment of being out on the bike.

At this level, it’s important to listen to your body and not let the pursuit of a high W/kg push you into fatigue and burnout. This will force you off the bike and your Watts per kilogram will quickly suffer.

Although it may be tempting to lose weight, if your fat levels are already low then you will simply eat into your muscle mass. The weight might come down, but it will come at the expense of a drop in power.

A smarter move is to include some targeted training sessions that help to boost maximal power output. Therefore, in addition to your regular riding, you should incorporate intervals, both long and short, and perhaps even some hill repeats.

The huge boom in indoor smart trainers over the last few years means that more and more cyclists can fit these types of training-specific intervals into their weekly plans without fear of missing out on those weekend coffee rides.

With a smart trainer, you don’t have to worry about finding a stretch of road without sharp bends and traffic and can really concentrate on the effort alone.

These sessions tend to be intense and put the body under a lot of stress. Make sure you factor in plenty of recovery time. Your muscles will thank you!

Watts per Kg: Healthy Eating

As cyclists sometimes we overlook the importance of diet as we tend to use all those miles to justify the odd calorie or beer here and there. Even the pros need the odd treat!

That said, sticking to a healthy diet and minimizing sugary and processed foods will have an impact on your W/kg, as well as just generally making you feel better. 

Any excess body fat is going to eat into those precious W/kgs. It just increases the denominator and adds nothing to your power.

A word of caution here. It is sadly all too common for cyclists at all levels to veer into a dangerous obsession with weight. This can have terrible consequences for your mental and physical health, not to mention your cycling performance.

Watts per Kg: Weight Training

Once upon a time, it was considered sacrilege by some cyclists to do any sort of exercise away from the bike.

Thankfully, cyclists these days tend to be a more enlightened bunch.

Cyclists can benefit hugely from adding some weight or resistance training into their routine. By targeting cycling-specific muscles, you can build muscle efficiency and endurance.

If you are just starting out with weight training, there’s no need for long gym sessions. Instead, start slow and concentrate on low-volume, low-weight sessions to prevent excessive time off the bike for recovery.

Watts per Kg: Cycling Efficiency 

To take full advantage of these physiological improvements it is vital that all the power is put through the bike and left on the road.

Make sure you spend time working on your pedaling technique, and book yourself in for a proper bike fit to really take advantage of those training gains out on the road.