How do I calculate a Metabolic Equivalent of Task (Mets) score?

How to Calculate a METs Score

One MET equals 3.5 mL of oxygen consumption per kilogram of body weight per minute (3.5 mL O₂/kg/min), representing the energy expenditure of sitting quietly at rest. 1

Basic Calculation Methods

Method 1: Direct Oxygen Consumption Measurement

• Divide the measured oxygen consumption (VO₂) by 3.5 mL/kg/min to convert absolute oxygen uptake into METs 2
• For example, if someone consumes 17.5 mL O₂/kg/min during activity, this equals 5 METs (17.5 ÷ 3.5 = 5) 1
• This requires metabolic measurement equipment (indirect calorimetry) to measure actual oxygen consumption 1

Method 2: Estimation from Activity Type

• Use standardized MET values from activity compendiums that list energy costs for specific activities 2
• Walking at 3-4 mph = approximately 3-4 METs 3
• Brisk walking at 4.8-6.5 km/h = 3-5.9 METs 1
• Running, swimming laps, or tennis singles = ≥6 METs 1

Method 3: Treadmill-Based Calculation

• Calculate METs from treadmill speed and grade using standardized equations, though this method has significant error 1
• At 0% grade: walking at 2.0 mph = 2.5 METs, 3.0 mph = 3.3 METs, 3.75 mph = 3.9 METs 1
• Each 2.5% increase in grade adds approximately 0.6-0.9 METs depending on speed 1
• For example, walking at 3.0 mph at 10% grade = 7.4 METs 1

Method 4: Heart Rate Ratio Method

• Calculate the ratio of exercise heart rate to resting heart rate, then apply regression equations to estimate METs 4
• This method shows correlation coefficients of 0.77 for group calibration and 0.93 for individual calibration 4
• Individual calibration is more accurate (error rate 1.64%-10.26%) than group calibration (error rate 0.07%-65.25%) 4

Intensity Classification Using METs

Absolute Intensity Categories

• Light intensity: 1.5-3.0 METs (slow walking, bathing, light household work) 1
• Moderate intensity: 3.0-5.9 METs (brisk walking, slow cycling, gardening) 1
• Vigorous intensity: ≥6.0 METs (jogging, running, swimming laps, singles tennis) 1

Age-Adjusted Considerations

• MET thresholds vary by age due to declining fitness with aging 3
• Young adults: moderate intensity = 4.8-7.1 METs 3
• Middle-aged adults: moderate intensity = 4.0-5.9 METs 3
• Older adults: moderate intensity = 3.2-4.7 METs 3
• Very old adults: moderate intensity = 2.0-2.9 METs 3

Calculating Total Physical Activity Volume

Multiply intensity (METs) × duration (minutes) × frequency to calculate total MET-minutes per week 1

• Example: 3 METs × 30 minutes × 5 days/week = 450 MET-minutes/week 1
• Alternatively, express as MET-hours: 3 METs × 0.5 hours × 2 times/day = 3 MET-hours/day 1

Important Clinical Caveats

Limitations of Standard MET Values

• The standard 1 MET = 3.5 mL O₂/kg/min is a convention that may not reflect actual resting metabolic rate for all individuals 1, 2
• Measured METs (using actual resting metabolic rate) differ from standard METs (using 3.5 mL O₂/kg/min) for most activities 5
• Compendium MET values differed from measured METs in 81% of activities tested 5

Individual Variability

• Holding treadmill handrails decreases the metabolic cost and underestimates true METs 1
• Body weight affects absolute energy expenditure: heavier individuals expend more total calories but similar METs for the same activity 1
• Fitness level matters: the same absolute activity (e.g., 3 METs) represents different relative intensities for fit versus unfit individuals 1

Measurement Accuracy

• Speed-based predictions are more accurate than accelerometer-based predictions for walking activities (explaining 10% more variance) 6
• Accelerometer output shows only moderate correlation (r = 0.65) with METs, making linear regression models inappropriate for accurate MET prediction 5
• Exercise capacity estimated from treadmill protocols has "significant degree of error" 1