Turn your power numbers into aerobic capacity
VO2max is the single most cited measure of endurance fitness, but a proper lab test is expensive and inconvenient. Cyclists have a shortcut: functional threshold power (FTP) is tightly linked to aerobic capacity, so a simple regression converts your watts and bodyweight into a credible VO2max estimate without a mask or a treadmill.
How it works
The tool first computes your power-to-weight ratio, then applies the standard cycling estimate:
power-to-weight = FTP_watts / bodyweight_kg (W/kg)
VO2max ≈ 10.8 × (FTP_watts / bodyweight_kg) + 7 (ml/kg/min)The constant 10.8 reflects the oxygen cost of producing one watt per kilogram on a bike, and the offset of 7 accounts for resting and baseline metabolism. Because the formula keys off watts per kilogram, two riders with the same W/kg get the same estimate regardless of absolute size.
Tips and example
A rider with a 280 W FTP at 70 kg has a power-to-weight of 4.0 W/kg. Plugging in: 10.8 × 4.0 + 7 = 50.2 ml/kg/min — a well-trained amateur level. Drop the same rider’s weight to 66 kg at unchanged FTP and W/kg rises to 4.24, lifting the estimate to about 52.8.
Notes: use a recent, honest FTP. The estimate assumes a typical cycling economy, so very efficient or inefficient riders will deviate. It is best used to track change over time — if your estimate climbs from 50 to 54 across a training block, your aerobic engine has genuinely grown even if the absolute number is approximate.
What a given VO2max means for cycling performance
VO2max is a strong predictor of cycling potential, but it interacts with two other factors — efficiency (how many watts you produce per milliliter of oxygen) and lactate threshold (the fraction of VO2max you can sustain for a long effort. Rough reference ranges for trained cyclists:
- Below 40 ml/kg/min: beginning or recreational cyclist
- 40–49 ml/kg/min: well-trained recreational, Cat 4/5 amateur racer territory
- 50–59 ml/kg/min: competitive amateur, Cat 3 racer, strong sportive rider
- 60–69 ml/kg/min: elite amateur to sub-elite professional
- 70+ ml/kg/min: professional road cyclist; grand tour domestiques commonly exceed this
Age matters significantly — VO2max declines roughly 1% per year after the mid-30s in sedentary individuals, and even well-trained athletes see gradual decline. A 55-year-old with a VO2max of 52 may be performing proportionally better relative to their age than a 28-year-old with 58.
How to improve your VO2max estimate
Two training approaches move the needle on aerobic capacity most effectively:
High-intensity intervals targeting VO2max. Classic formats include 3–8 minute efforts at a power output near your current VO2max pace (roughly 105–120% of FTP), with equal or shorter recovery periods. These intervals drive cardiac adaptations — stroke volume, cardiac output — that directly lift the ceiling. A common format: 5 × 4 minutes at 110% FTP with 4 minutes easy recovery.
High training volume. Aerobic base built from consistent moderate-intensity riding over months and years raises VO2max by developing mitochondrial density, capillarization, and aerobic enzyme activity. This is the foundation on which high-intensity intervals operate.
Honest FTP: why it matters for this estimate
The estimate is only as accurate as the FTP you enter. Common FTP testing errors:
- Using a 20-minute average without the 5% correction. A true 20-minute test is harder than a threshold effort; multiply the 20-minute average by 0.95 to estimate FTP
- Using an FTP from a different season. FTP changes significantly with training block, rest, and time of year — a summer FTP used in winter underestimates current fitness
- Ramp test without understanding the protocol. A ramp test result is already corrected; do not apply an additional factor
Enter your most recent, correctly calculated FTP for the most meaningful estimate.