Everything You Need to Know About Power to Weight Ratio

This is a good time to explore the idea of power-to-weight ratio, or PWR. In simple terms, PWR is a way of comparing two riders of different weights to predict which one has the potential to go uphill faster. When the pitches get steep and the mountain passes get long, the riders with higher PWR values have a big advantage. Here’s what you need to know about this critical performance marker:

The Basics of Power-to-Weight Ratio

Larger riders have more muscle and can generate higher absolute power outputs, but they have more mass to drag uphill. Smaller riders have less mass to accelerate against gravity, but carrying less muscle also means lower absolute power outputs. Riders who excel on the toughest climbs are small, lightweight riders who have high power outputs.

But it’s important to remember that PWR isn’t a static number. Rather, it’s a number that corresponds with a specific time. For instance, 5.5 watts/kg for 30 minutes. For 60 minutes that same rider would average lower, like 5.0 watts/kg; and average higher, maybe 6.0 watts/kg, for 15 minutes.

To determine a rider’s PWR over a specific duration, you divide the rider’s weight in kilograms into the average power from the effort. Example: Rider A weighs 76 kg and averaged 275 watts for a 20-minute climb, so his PWR for 20 minutes is 3.6 watts/kg.  Rider B weighs 55kg and averaged 210 watts for the 20-minute climb and has a PWR of 3.8 watts/kg. Despite producing far less power, the 55-kg rider would be further up the climb after 20 minutes. Or put another way, Rider B should be able to drop Rider A.

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Is Lighter Always Better?

This is a common question related to climbing. Generally speaking, lighter is better, but an athlete can be too light. You’re not likely to see this at the Tour de France because the riders have a great understanding of their optimal race weights, but in the amateur ranks, we do see riders who obsess about weight loss until they become so light they actually harm their performance.

Extremely light athletes struggle to maintain consistent high-quality training and are more susceptible to illness, often because they’re not providing their bodies with enough energy to support their immune system and recover from their efforts. When you catch the situation early, a rider can often return to optimal performance by regaining as little as 1-2 kilograms.

Does the Weight of the Bike Get Factored In?

Not typically, because at the pro level the assumption is that the bikes weigh the UCI limit of 6.8 kilograms. In principle cutting weight on the bike will effectively increase your PWR, but the danger with factoring bike weight into your numbers is that it provides athletes with a way to “buy” their way to their goal PWR. That means they often stop working to optimize power output and bodyweight. For most people, it’s better to maximize PWR regardless of the bike, and then consider weight-savings on the bike as an added race-day advantage.

Does Power-to-Weight Ration Change Throughout the Year?

Yes, and that’s perfectly normal. Elite racers aim to be as strong as possible when they are also as light as they can be, but this is a delicate balance that can’t be maintained for very long. Nonetheless, throughout the year they try to keep fluctuations in either bodyweight or power output relatively small because gaining weight or losing power means a lot of work to get back to your peak. Experienced amateur cyclists can expect to see a 15% change from the lowest to highest PWR they see during the year, and pros aim for a smaller fluctuation.

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Which Is More Important, Losing Weight or Gaining Power?

For novice cyclists and experienced riders who are carrying around more than 10 extra pounds, losing weight and gaining power are equally important and equally achievable. This also means that heavier cyclists can make bigger improvements in their PWR because they have more room to attack both parts of the equation.

Let’s use a local Colorado Springs climb as an example. Cheyenne Canyon is a 5-kilometer climb with an average 8% grade. Our example rider weighs 75kg with a max sustainable power of 250 watts. Dropping 2.5 kilograms (roughly 5 pounds) with a power output of 250 watts would cut 38 seconds off this rider’s time. Improving power output by 10 watts without any weight loss cuts 41 seconds off his time. This increases to 85 seconds if you improve power output by 20 watts. When you combine losing 2.5 kilograms of bodyweight with a 20-watt increase in sustainable power (both of which are attainable for most cyclists), this rider would go 2:03 faster up Cheyenne Canyon.

Pro cyclists have pretty much maxed out both sides of the PWR equation and they are just about as lean and as powerful as possible. On major climbs, though, that’s why other factors like hydration status, core temperature regulation, and even positioning in the group make such a difference. If a rider can stay cool, stay hydrated, and avoid unnecessary accelerations then he may have more power in reserve to take advantage of his PWR at a crucial time.

Does Power-to-Weight Ratio Stay Constant During a Grand Tour Like the Tour de France?

No. Remember, PWR is not a static number. It depends on the duration of the climb, how many hours of racing have been done before that specific climb, how aggressively a particular stage or climb is contested, wind direction, temperature, and even humidity. As riders get tired, overheated/chilled, or dehydrated, PWR goes down. A climb with moderate temperatures, a tailwind, and really aggressive racing can result in high PWR values. By the final climbs of long stages and the last mountain stages of the race, even the leaders’ PWRs can drop to around 5 watts/kilogram. In early mountain stages – or for shorter periods within later climbs – they will be around 6 watts/kg.

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Where Does Power-to-Weight Ratio Make the Biggest Difference?

Power-to-weight ratio makes a difference anytime you have to accelerate, which is why even large sprinters try to stay lean, too. For the climbers and yellow jersey contenders, PWR is most crucial at the steepest parts of big climbs. When the grade is steep, having a higher PWR gives you the ability to accelerate more sharply, which means it provides the opportunity to launch scorching attacks. Riders with lower PWR values can’t accelerate as quickly, but may be able to reel you back in when the climb is less severe.

Comments 14

  1. Thanks for a great article! I’m female, about 58kg and have been working on increasing my power to weight ratio on a Watt bike. However, my biggest race next year (triathlon) is on the flat, should I be doing something different. Would it actually do me good to gain a few pounds rather than try to lose them? Thanks ever so much for the advice! Stephanie.

  2. What about those of us who lose weight without trying? As I get older, I’m getting SKINNIER (about 5 kilos less than a few years ago). My power AND speed has dropped on my “uphill time trial.” (Its not for lack of calories . . . I eat 4-5 platefuls at the local buffee! And eating more just makes me move my bowels more.) And yes, my blood tests are normal. Any ideas on how to gain back that extra kilo or to to get me up to “full speed?”

    1. I’m guessing — most would say “wish we had that problem”. If you’re not doing major workouts (or working out at all), and also are eating a good 2500+ calories, then you shouldn’t be losing weight. If so — you might want to get a medical checkup.
      Of course — if your doing the equivalent of the Tour de France (6000+ calories per day) — well of course you have to eat more — WAY more!

  3. So, here’s the extra question part. The weight part is pretty obvious. How about the power part.
    — How does one go about gaining it?
    — Go about keeping it (sustaining over weeks, months, years)?
    — And isn’t there also just a genetic component going on here — some people
    are never going to get to their desired power level?

  4. Great article as usual, Chris.
    Obviously, more power is good, and less weight is good (up to a point).
    What I have always wondered is…how gradient fits into the PWR equation. For example…
    As the gradients get really steep (e.g. above a 10% gradient), a 5% loss in weight will likely become more important than a 5% increase in power in terms of increasing your climbing speed. This is where the really small riders can excel on climbs (e.g. Nairo Quintana & Joaquim Rodriguez).
    Conversely, for shallower gradients (e.g. less than 5%), a 5% increase in power will likely see your speed increase more than through a 5% drop in weight. This is where the tall but slim power-houses can excel on climbs (e.g. Tom Dumoulin & Brad Wiggins a few years ago).
    Therefore, do you know of any any research which helps to quantify how the gradient of a climb factors into the PWR equation, and where the tipping point is in terms of gradient when power and weight are of equal importance?
    Best regards,

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  6. Good explanations and examples.
    Whatever your current PWR you’ve got three performance barriers to over come
    Hydration, Fueling and Cooling.
    Fall behind on any of these and power and endurance falls quickly.

  7. Hi Chris,
    Enjoyed the PWR article but it destroys my theory of why I am able to out climb other serious bikers. I am a weekend rider at best and carry 50-75 pounds over others. During the flat portions of the rides I have to push it to keep pace but once the climbing begins I find myself at the front. I find it very difficult to go as slow as most are comfortable with during climbing workouts. I assumed my climbing was because I was able to put so much more weight on the pedals.

    1. Just some initial thoughts Jeff…
      Possibly poorer aerodynamics than your friends on the flat (e.g. higher riding position, or looser-fitting clothing).
      Also, if the climbs are not too steep, your extra weight won’t penalise you too much.
      Additionally, some people can put out a lot more power in a climbing position than they can in a flat-terrain position (either naturally, or due to spending a lot more time cycling in a climbing position).

    2. It also depends on what sort of climb you are doing. As per the original article power/weight also has a time dimension. On short sharp climbs that only take a minute or two at most power is really the most important. These are the sort of climbs you see in the early season “classics” and these are often best handled by relatively chunky riders not out and out climbers.

      For this sort of climb your theory about weight is not altogether wrong. If you tackle them by standing and shifting your body from side to side you extra pounds will produce more power. But only for a relatively short time, this sort of approach is inefficient and you will quickly tire.

      Weight>Power really comes into its own on longer climbs that take many minutes or hours. It would be extremely surprising if you can drop your mates on these sorts of climbs while giving them 50-75lbs.

      If you do then the reason will most likely not be physiological but mental, there is no hiding place on climbs and often the difference between winners and losers is not just w/kg but also how you deal with the unrelenting pain.

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  9. I’m curious if the same principles apply to a time trial? Specifically does PWR have the same affect on a flat 20 or 40k TT?

  10. Hi Chris,
    My wife and I have been riding racing for over 20 years. We spent a couple winters working out in your Tucson facility, we live in Tucson. She is 5′-1″ 120 lbs and I’m 6′-3″ 185 lbs. strangely enough we have almost identical PWR to weight numbers, about 3.25 watts/Kg, yet I consistantly out climb her when doing long climbs like Mt Lemmon. Shouldn’t she be able to leave me behind on the long climbs or is it possibly more about duration that each of us can hold a specific power? Thanks. Enjoying your TDF articles and looking forward to this winter and more sessions at your wonderful facility just 3 miles from our home.
    Jeff & Carolyn

    1. If you have the same W/kg as your partner uphill you’ll be similar speeds… but you weigh more, so your absolute power is higher, on the flat they are going harder than you relative to their absolute power being lower. When you hit the climb you will be fresher. Also males are not comparable to females and visa versa completely different physiology. Then there’s the fact a watt is not just a watt. Depending on muscle fibre makeup some people can put more power down on the flats or the climbs.

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