Enter the power in Watts and the body weight in kilograms into the calculator to determine the Metabolic Equivalent. This calculator can also evaluate any of the variables given the others are known.
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Watts To METs Formula (ACSM Leg Ergometry)
This calculator uses the ACSM (American College of Sports Medicine) leg-ergometry metabolic equation, which is the standard clinical formula for stationary cycling on an upright or recumbent bike:
METs = 2 + 3.147 x (W / kg)
Where W is the mechanical power output in watts, and kg is the rider's body mass in kilograms. The constant 2 accounts for resting metabolism plus the oxygen cost of unloaded pedaling (moving the legs without resistance), and 3.147 is derived from the ACSM's VO2 coefficient of 10.8 mL/kg/min per watt, divided by 3.5 mL/kg/min (the value of 1 MET). This formula is validated for steady-state cycling between approximately 50 and 200 watts.
The underlying VO2 equation from which this MET formula is derived is:
VO2 (mL/kg/min) = (10.8 x W) / kg + 7
The 7 mL/kg/min baseline represents 3.5 mL/kg/min of resting oxygen consumption (1 MET) plus 3.5 mL/kg/min for the cost of moving the legs against zero resistance. Dividing the entire equation by 3.5 converts VO2 into METs.
| Watts per kilogram (W/kg) | METs |
|---|---|
| 0.25 | 2.79 |
| 0.50 | 3.57 |
| 0.75 | 4.36 |
| 1.00 | 5.15 |
| 1.25 | 5.93 |
| 1.50 | 6.72 |
| 1.75 | 7.51 |
| 2.00 | 8.29 |
| 2.25 | 9.08 |
| 2.50 | 9.87 |
| 3.00 | 11.44 |
| 3.50 | 13.02 |
| 4.00 | 14.59 |
| 4.50 | 16.16 |
| 5.00 | 17.74 |
| 6.00 | 20.88 |
| 7.00 | 24.03 |
| 8.00 | 27.18 |
| 9.00 | 30.33 |
| 10.00 | 33.47 |
| * Rounded to 2 decimals. ACSM leg-ergometry formula: METs = 2 + 3.147 x (W/kg). | |
What Is a MET?
A MET (Metabolic Equivalent of Task) represents the ratio of an activity's metabolic rate to the resting metabolic rate. By convention, 1 MET equals an oxygen consumption of 3.5 mL of O2 per kilogram of body weight per minute, which is approximately 1 kcal per kilogram per hour. Sitting quietly at a desk registers at about 1.0 MET, while vigorous cycling can exceed 12 METs.
The 3.5 mL/kg/min reference value was originally measured in a single 40-year-old, 70 kg male subject and later adopted as a universal constant. In practice, actual resting VO2 varies by age, sex, body composition, and fitness level. Studies have shown that resting VO2 in obese individuals can be as low as 2.6 mL/kg/min, while highly fit athletes may rest at 4.0 mL/kg/min or higher. This means the same wattage on a bike can represent different true MET values depending on the individual, and the calculator's output should be treated as an estimate anchored to the standardized 3.5 mL/kg/min convention.
MET Intensity Zones for Cycling
The Compendium of Physical Activities (2024 update) classifies exercise intensity by MET level. Understanding where your cycling effort falls helps with exercise prescription, cardiac rehabilitation programming, and training periodization.
| Intensity Zone | MET Range | Cycling Context | Approx. W/kg |
|---|---|---|---|
| Sedentary | 1.0 - 1.5 | Sitting on a stationary bike, no pedaling | n/a |
| Light | 1.6 - 2.9 | Very easy spin, minimal resistance | < 0.3 |
| Moderate | 3.0 - 5.9 | Casual road riding, 10-12 mph flat terrain | 0.3 - 1.2 |
| Vigorous | 6.0 - 8.9 | Brisk group ride, 14-16 mph | 1.3 - 2.2 |
| High | 9.0 - 11.9 | Competitive training, sustained climbing | 2.2 - 3.1 |
| Very High | 12.0+ | Racing, time-trial, sprint intervals | > 3.2 |
| W/kg values derived from ACSM formula. Real-world road cycling METs will differ due to wind resistance, terrain, and drivetrain losses. | |||
Mechanical Power vs. Metabolic Power
A common source of confusion is the difference between the watts displayed on a bike computer (mechanical power) and the total metabolic energy the body actually consumes. The human body converts food into mechanical work at roughly 20-25% gross efficiency during cycling. A rider producing 150 W of mechanical power at the pedals is consuming approximately 600-750 W of metabolic energy. The remaining 75-80% is released as heat, which is why cycling in warm conditions causes such rapid thermal stress.
The ACSM formula used in this calculator accounts for this inefficiency internally. It was derived from direct measurements of oxygen consumption during ergometer cycling, so the watts you enter are mechanical watts (what your power meter reads), and the formula already produces the correct metabolic MET output. You do not need to adjust for efficiency yourself.
Why Body Weight Matters in the Conversion
Unlike running, where moving your body mass is the primary source of work, stationary cycling decouples body weight from mechanical output. Two riders at 100 W produce identical mechanical work, but a 60 kg rider is working at 1.67 W/kg (about 7.3 METs) while a 90 kg rider is at 1.11 W/kg (about 5.5 METs). The heavier rider's absolute oxygen consumption is higher, but relative to their body mass, the metabolic demand per kilogram is lower. This is why MET-based exercise prescriptions in clinical settings always require body weight as an input alongside power.
This also means that two people cycling at the same MET level are at the same relative physiological strain, even though their absolute wattages differ. A cardiac rehabilitation patient prescribed exercise at 4 METs can use this calculator to find their personal target wattage based on their body weight.
Limitations and When This Formula Does Not Apply
The ACSM leg-ergometry equation is validated for steady-state cycling between 50 and 200 watts on a mechanically braked cycle ergometer. Outside that range, or in different exercise contexts, accuracy decreases. Arm-crank ergometry uses a different ACSM equation with a higher oxygen cost coefficient: VO2 = (18 x W) / kg + 3.5, reflecting the lower mechanical efficiency of upper-body exercise. Rowing engages both upper and lower body simultaneously, producing 10-15% higher energy expenditure than cycling at the same external wattage.
Outdoor cycling introduces additional variables not captured by the formula. Aerodynamic drag, rolling resistance, gradient, wind speed, and drivetrain friction all affect the relationship between metabolic effort and power meter readings. A rider producing 200 W into a 30 km/h headwind is doing the same metabolic work as one producing 200 W on a calm day, but the perceived effort and speed differ dramatically. For outdoor riding, power meter data combined with this formula provides a reasonable MET estimate, but GPS-based calorie estimates from cycling apps use different models that attempt to account for terrain and conditions.
Sprint and anaerobic efforts (above about 200 W for most riders) increasingly rely on anaerobic metabolism, where the linear relationship between watts and oxygen consumption breaks down. The formula progressively overestimates METs at very high power outputs because it assumes a purely aerobic steady state.
METs to Calories: The Connection
Once you know the MET value of your cycling session, estimating calorie burn is straightforward. The standard formula is: Calories per minute = (METs x 3.5 x body weight in kg) / 200. This calculator's Calories tab performs this computation automatically. For a 75 kg person cycling at 6.7 METs (about 1.5 W/kg, or 112 W), calorie burn is approximately 8.8 kcal/min, or 528 kcal per hour. These values represent gross energy expenditure, including the calories you would burn at rest regardless of activity.
