METs, short for metabolic equivalents of task, is a unit that measures how hard your body is working during any physical activity. One MET equals the energy you burn while sitting quietly, roughly 3.5 milliliters of oxygen per kilogram of body weight per minute. An activity rated at 5 METs means your body is working five times harder than it does at rest. The term shows up in exercise guidelines, fitness trackers, and medical settings like cardiac stress tests.
There’s also a completely different use of the word: in cancer care, “mets” is informal shorthand for metastases, meaning cancer that has spread beyond its original site. Both meanings come up frequently in health conversations, so context matters.
How METs Measure Exercise Intensity
METs give a standardized way to compare how demanding different activities are, regardless of who’s doing them. Sitting on the couch is 1 MET. Washing dishes might be around 2. Brisk walking lands somewhere around 3.5 to 4. Running at a 10-minute-mile pace is roughly 10 METs. The harder the activity, the higher the number.
Health guidelines break these numbers into three tiers:
- Light intensity: below 3.0 METs (casual walking, light housework)
- Moderate intensity: 3.0 to 5.9 METs (brisk walking, cycling at a relaxed pace, gardening)
- Vigorous intensity: 6.0 METs or higher (running, swimming laps, heavy yard work)
These cutoffs are the foundation of public health recommendations. When you hear that adults should get 150 minutes of moderate-intensity exercise per week, that translates to about 500 MET-minutes: 150 minutes multiplied by activities in the 3.0 to 5.9 MET range. Additional health benefits continue to accumulate beyond 1,000 MET-minutes per week, following a dose-response pattern where more activity yields more benefit.
How to Estimate Calories Burned With METs
If you know the MET value of an activity and your body weight, you can estimate calorie burn with a simple formula: multiply 0.0175 by the MET value, then multiply by your weight in kilograms. The result is calories burned per minute.
For example, a 70-kilogram person (about 154 pounds) doing an activity rated at 6 METs would burn roughly 7.4 calories per minute (0.0175 × 6 × 70). Over a 30-minute session, that’s about 220 calories. This is the same math that many fitness trackers and gym machines use behind the scenes, though individual factors like fitness level and body composition can shift the real number up or down.
METs in Cardiac Stress Tests
During a treadmill stress test, doctors gradually increase the speed and incline while monitoring your heart. The goal is to see how many METs you can achieve before fatigue, symptoms, or heart rhythm changes stop the test. Your MET score reflects your functional capacity, essentially how well your heart and lungs can deliver oxygen under increasing demand.
The benchmarks are straightforward:
- Below 5 METs: poor exercise capacity
- 5 to 8 METs: fair
- 9 to 11 METs: good
- 12 METs or higher: excellent
These numbers carry real clinical weight. A score below 5 METs may prompt further imaging to evaluate the heart more closely, and it factors into decisions about surgical risk and cardiac rehabilitation. After a heart attack, early stress tests are often capped at 5 METs to safely gauge whether the heart can handle low-level exertion before a patient returns to normal activity.
Why Your MET Capacity Matters for Longevity
Your peak MET capacity isn’t just a fitness score. It’s one of the strongest predictors of how long you’ll live. A large meta-analysis published in JAMA found that every 1-MET increase in a person’s maximum exercise capacity was associated with a 13% reduction in the risk of dying from any cause. That held true for both men and women across a range of ages and baseline health levels.
This is part of why doctors care about the number on your stress test. A person who can reach 10 METs has a meaningfully different risk profile than someone who tops out at 5, even if neither has obvious heart disease. The practical takeaway is that improving your aerobic fitness, even modestly, shifts the odds in your favor. Moving from “poor” to “fair” on the MET scale represents a real change in cardiovascular risk.
“Mets” in Cancer: A Different Meaning
In oncology, “mets” is shorthand for metastases. When cancer spreads from its original location to distant organs like the lungs, liver, bones, or brain, those new sites of disease are called metastases. You’ll hear patients, caregivers, and sometimes clinicians refer to metastatic cancer simply as “mets,” particularly in breast cancer communities where the term is widely used.
Metastatic cancer is generally classified as stage IV, meaning the disease is no longer confined to one area. The distinction matters because treatment goals and approaches change significantly once cancer has metastasized. If you encounter “mets” in a medical report or conversation about cancer, it refers to this spread rather than anything related to exercise or metabolism.