Watts To METs Calculator

Watts To METs Formula (ACSM Leg Ergometry)

This calculator uses an ACSM-style stationary leg-cycle ergometer estimate with 6.12 kgf·m/min per watt. It estimates standardized oxygen cost and METs, rather than measuring personal metabolism:

Where W is the mechanical power output in watts, and kg is the rider's body mass in kilograms. The 2-MET intercept includes rest plus unloaded pedaling. The coefficient is 11.016/3.5 = 3.147428571…: 11.016 comes from 1.8 × 6.12. The widget previously rounded this to 3.147. A 6.0 conversion instead gives 10.8/3.5, a different convention. This estimate is commonly applied to submaximal steady-state stationary leg cycling at about 50–200 W; cadence is not modeled.

The underlying VO2 equation from which this MET formula is derived is:

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.

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 value is a standard convention. Measured resting oxygen consumption varies with age, body composition and other factors. Standard METs do not measure an individual’s actual resting metabolism or relative exercise strain.

MET Intensity Zones for Cycling

The table below shows the descriptive bands used on this page. The extra High and Very High subdivisions are not a personalized clinical classification or a Compendium activity lookup. Its context labels and approximate W/kg ranges do not predict road speed or individual exercise strain.

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 estimates standardized metabolic METs under its assumptions. 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 7.2 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 model uses body mass alongside mechanical power; its output is not an individualized exercise prescription.

Equal standard MET values do not ensure equal relative physiological strain: individual fitness and measured oxygen capacity are not inputs. The reverse-power calculation is algebraic model matching, not a personal training target or cardiac rehabilitation prescription.

Limitations and When This Formula Does Not Apply

The leg-cycle estimate is commonly applied to submaximal steady-state stationary cycling around 50–200 W. It does not model cadence, and predictions can be less accurate at higher cadences or outside that workload range. Arm cranking, rowing and other activities require their own estimation methods.

Outdoor cycling adds road loads and conditions that this stationary model does not resolve. Power-meter readings can supply mechanical power, but the equation does not determine speed, individual efficiency, perceived effort or actual metabolic expenditure in those conditions.

The 200 W scope marker is not a universal anaerobic threshold. Sprint and other non-steady-state efforts can involve energy pathways that a steady-state oxygen-cost equation does not capture; results outside the model’s usual scope are extrapolations.

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. The Gross energy (kcal) mode performs this estimate from the selected source and duration. 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.