Estimating Your FTP

If you train with a power meter (highly recommended) then you probably know that setting up power training zones is best based on your Functional Threshold Power (FTP). That’s the average maximal power you are capable of sustaining for one hour. I’ve written here many times before describing how to do a field test to find your FTP. Here's one of those posts.

Athletes often ask me what their FTP should be. That’s hard to answer because (as usual) there are so many “it depends.” But here’s a quick and dirty way to estimate what your FTP based on body weight, age and gender…

Step 1. Double your body weight in pounds (1 kg = 2.2 lbs). Example: A body weight of 154 pounds (70 kg) estimates an FTP of 308 watts (154 x 2 = 308).

Step 2. Subtract 0.5% for every year beyond age 35. Example: If the above 154-pound rider is 50 years old he would subtract 7.5% from 308 (50 – 35 = 15 x 0.005 = 0.075). This would predict an FTP of 285 (308 x 0.075 = 23.1, 308 – 23.1 = 284.9).

Step 3. Women riders can subtract 10% from the estimated FTP as found in steps 1 and 2 above. Example: A 120-pound (54.5-kg) woman who is 40 years old would have an estimated FTP of 211 watts (120 x 2 = 240, 240 – 2.5% = 234, 234 – 10% = 210.6).

If your actual FTP based on testing falls short of the estimation then you may have a new training objective for this winter. If your known FTP exceeds the estimation then congratulations for doing something right in your training. (In a future post I’ll discuss how to train to raise your FTP.)

Not all of the possible variables are included in the 3-step estimation above. There could well be others. One of the most significant for some athletes is altitude. As the altitude increases above sea level aerobic capacity declines which means that one’s average max power over a one-hour period would also decline. For example, at 5,000 feet (1,516 meters) the negative effect of altitude is between 5% (acclimated to altitude) and 9% (not acclimated) according to Bassett et al, 1999. So an FTP determined in Boulder, Colorado would be roughly 5-9% greater at sea level. Example: Our 50-year-old rider from above is going from Boulder to sea level for a race and wants to know what his power zones should be at the lower altitude. Since he lives at altitude we can assume he is acclimated. So if we add 5% to his altitude FTP of 285 the new FTP is estimated at 300 watts (285 x 0.05 = 14.25, 285 + 14.25 = 299.25). He would then reconfigure his power zones based on an FTP of 300.

Of course, if you are going to altitude from sea level to race you would subtract the estimated power change to reconfigure your zones. (I’ll post an altitude adjustment table based on Bassett’s study in an upcoming blog.)

And, of course, excess fat or muscle, especially upper-body muscle, will also skew the results. If you have a considerable amount of either of these then your estimated FTP is likely to be too high. Knowing lean body mass from testing would be a better predictor if fat is an issue. That won’t help for overly muscular riders, however. (Side note: While the weight of your bike is often not included in the power-to-weight ratio it certainly is an issue. A heavy bike will diminish the effect of an otherwise high FTP estimated from body weight. This is a real issue for a small woman. A 15-pound (6.8 kg) bike is a heavy load to carry uphill for a small rider. But it’s still not included in the estimation of FTP.)

I’m certain there are even more variables, such as experience in the sport and familiarization with the testing protocol, which I have don’t know how to include in the estimation of FTP. And the above method is not scientifically proven. It’s just something I’ve come up with from coaching a small number of riders and talking with others. But give it a try to see what your FTP estimation is. I’m curious to see how far off it is from what you have found your actual FTP to be.

Comments

[Bill]

Hi Joe,

Is it possible, or even recommended to estimate your FTP based upon recent races / hard training workouts?

Thanks!
Bill

[Endurants.wordpress.com]

Hmm. I've done a fair amount of FTP testing and I'm not sure about the weight x 2 estimation, Joe. It certainly 'feels' like such a quick and dirty FTP estimate is difficult and prone to a wide range of interpretation errors. E.G. I am 178lbs (80.74kg) and currently have a 30' threshold of 295-300 watts, determined using a 30' computrainer-based test on a flat course (i.e. no hills). Using the "quick and dirty" method of weight x 2, I can tell you there is NO way I'm hitting 356 watts as my threshold, probably ever.

And you preach power-to-weight anyway as the key metric, so isn't FTP somewhat irrelevant as a standalone number?'

-Henry

[Linda]

Not too close for me: calculation says 190 and a 20' FTP test gave me 160. Female, 52, living at 5000'.

[Tim]

Hi Joe--I'm in Ironman training and have been enjoying your books and online posts. Does this estimation technique get skewed for people who are at the extremes for normal height? I'm 6'6, weigh 210lbs and in my late 20s. My FTP, according to tests done on a power meter, is around 300, but according to your estimation should be about 420. That's a pretty big difference!

Is it similar to the standard BMI tests? Even though I have a bodyfat percentage of about 10% or so, according to BMI calculators I am considered almost overweight.

I realize your post is just a general estimation...Thoughts?

Thanks!

[Roy Galvin]

Actual FTP = 273w / Est FTP = 303w

[Joe Friel]

Tim--Height could be another variable. I simply haven't worked with many very tall athletes. A couple of years ago I coached a 6'8", 200-lb IM tri. The formula was close for him but predicted about 20w high if I recall right.

[Joe Friel]

Henry--It is certainly possible that this doesn't work for most riders. It just seems to have worked fairly well for those I've coached the last few years. FTP irrelevant? Not at all. it provides a standard upon which to based train zones.

[Joe Friel]

Bill--FTP is best based on a stand alone bike race that took about an hour to complete. In the absence of that a 30-minute TT done solo will serve as a proxy. For more details on this (I've explained it here at least 5 times in the last year) go to the home page of my blog (www.joefrielsblog.com) and do a search on FTP.

[Ken]

Based on your formula, young folks 'should' have an FTP of 4.4 watts/kg. As it happens, that has been my goal for the past year, though I am well beyond age 35, and still pretty far off. This is the middle range of cat 2 racers according to the Coggan grid (http://home.trainingpeaks.com/...owerprofiling_v4.xls). Although I suspect the Coggan graph underestimates the average power in the cycling categories, I wonder whether your 'should' formula might be a bit high for most mortals, as you suggest.

On a related point, at the risk of being critical, the social scientist in me is unsatisfied with 'rules of thumb' formulas and ranges such as these, and especially the one for 'training stress score,' because they appear to be based mostly on personal experience and intuition rather than scientific testing. Perhaps it is too much to ask, but it would be nice if an enterprising young exercise physiologist were to develop more scientific measures or ranges of power-based effort. Just a thought.

[Ken]

Sorry - Here is the correct link: http://home.trainingpeaks.com/media/69406/powerprofiling_v4.xls

[Martin]

nteresting, not seen a rough rule of thumb measure of FTP like this before.

In my case as it happens I am the 50 year old 154lb rider so my theoretical FTP works out at 285W. My actual FTP is in fact 300W.

However as you mention fat will affect the calculation. The above power is peak season when I am around 12% fat. At other times of the year my body weight will be higher due simply to more fat.

If you were to do the calculation start of training when I weigh 7-10lbs more it would be pretty close.

That said my results put me top 5% of competitive riders. This is partly because I train hard but also, more fundamentally, because I have the luck to be born with a better than average set of genes wrt FTP.

My guess is that while in right ballpark the calculation overestimates the FTP potential of the population as a whole as some of the other feedback above indicates.

[Jo]

I see that the estimation turned out higher for most ppl who commented. Mine was lower. 45kg = 99x2 = 198-10% = 178w. My FTP from tests is around 210w - 222w depending on build phase. I live at abt 1700m altitude & have been cycling close on 3 yrs now, racing for 1.5yrs.

[Keith]

Pretty close for me, at least when I'm well-trained. The formula predicts an FTP of 276W; a good recent test for me was 268W.

[guy]

Oh I'm low. I'm tall and have a lot of upper-body bulk, but still ouch... That follow up on how to increase one's FTP will be quite welcome!

[Sérgio Chaves]

Hi Joe! My FTP calculated by your formula is lower than that measured in the test bike. According to your formula, my FTP should be 343W, but in reality is 390W. I am above 47W. I started this season with a FTP of 345W. I must say that coach Rob Kelly is doing a great job with me.

[brian]

Quick, dirty and very inaccurate. It would be much easier (and accurate) to glance power distribution over the last 28d. Even using MMP would yield more accurate results.

[Matthew Perry]

So basically what this boils down to is that, for every age/gender group there is a target w/kg ratio? 4.4 w/kg for a <35 male for instance. And being above or below this threshold has some sort of meaning in the relative sense?

My FTP (estimated by lots of field testing) is about 345 at 5k above sea level. My FTP (estimated by this formula) should be roughly 360 +/- 10 watts. So, given the altitude effects, it seems close enough ... but what does it mean? I could either be undertrained or at the peak of my potential. Being spot on this 4.4 w/kg mark doesn't really tell me much other than coincidence.

Isnt a simple 30 minute field test going to tell you a lot more?

[Joe Friel]

Brian--yes, I agree that it's certainly not perfect. There are many ways to estimate FTP. I was just trying to show one more rough possibility to get the athlete in the ballpark. And actually, I've found it to be quite a small ballpark for road cyclists, bigger for triathletes.

[Joe Friel]

Matthew--Or even better yet do a 60-minute TT. Or how about a lab test with gas analysis and lactate draws instead. You're right--there are more accurate methods. No doubt about it. My purpose was not to give every rider out there his/her exact, spot-on FTP. It's just a very rough gauge which seems to be pretty close for many. Roughly +/- 10% for most roadies. Maybe +/- 20% tris. And probably quite high for most of them. Kind of like estimating LTHR based on RPE. Not perfect but decent-sized ballpark.

[Rayomand]

Dear Joe, thanks for this post as I needed some stuff on training with Power; In Training Bibile this area isnt as eloborative.

An Unrelated Q/s to this topic - I am having pain with my Left upper knee just in dead center before the knee cap starts usually when i am doing high gear low cadence. Have also tried to slide on edge of seat while riding. Can you please throw some light on the reason - I suspect it is due to bike seat position as i recently got the knee check up done and it was all clear.
Thanks
Rayomand

[Joe Friel]

Rayomand--It sounds like patella-femoral syndrome. Quite common for cyclists when doing high gear, low cadence work. And yes it could be due to saddle position. The most common position causes are a saddle too low or too far forward. It could also be related to Q angle (essentially, feet too wide relative to knees, hips). There are other possibilities. The best options are to see a physical therapist who works with cyclists and/or a bike fitter who knows cycling biomechanics and physiology quite well. in the mean times it's probably a good idea to avoid anything that aggravates it. Don't allow it to become chronic or you could have it for a very long time. Good luck with it.

[Ted]

What is the role of V02 max and %V02 max here, Joe? Your calculation assumes two men (or women) of the same age and weight would have the same FTP or FTP potential, if trained. I wish my FTP was as high as your calculation suggests!

[Joe Friel]

Hi Ted, I expect we'd find that if we studied VO2max and FTP that there is a fairly close relationship. In other words, the higher the VO2max the higher the FTP. Never seen any research on that, however.

[David]

Surprisingly close for me. I'm 43, 6'-3" and a lean 178 lb. The formula gives 342W. I live at sea level and a recent best 20 minute average from a hill-climb TT was 320W. If I scale that up by 5-9% for the 5k' elevation, I get 336-349W, which perfectly straddles the estimate.

[Glenn]

Calculated 308W 30Y M living at 2000ft. Tested on road at 306W FTP.

Interesting. Are you also suggesting that if I were to have an FTP of 260 for example I'm well below my potential based on this model?

Is it more a model of FTP potential?

If so does this suggest I couldn't do much better? Having just started working on FTP specifically, I'm jeen to get up near 320-330W.