Understanding Watts and METs: Core Concepts and Differences

What are Watts in Fitness Equipment?

Watts are a unit of power, representing the rate at which work is done. On fitness equipment, watts quantify how hard your body is pushing against the machine’s resistance in real time. In cycling ergometers, for example, the power output is calculated as torque multiplied by angular velocity, yielding a numerical readout such as 100 W, 200 W, or higher. This fixed unit of power provides a direct, comparable measure of effort across sessions and athletes, independent of pace or heart rate alone.

Power meters on bikes can be crank-based, pedal-based, or hub-based, and some machines estimate power through algorithms when a true meter isn’t available. The key point is that watts reflect instantaneous power delivery to the equipment, which translates into training stress. For trainers and gym users, watts offer a precise target for workouts, enabling repeatable progression and objective benchmarking over weeks and months.

Because watts are a rate, two riders producing the same watt value may experience different perceived effort due to biomechanical efficiency, fatigue, and technique. Consistency in the device and calibration is essential; otherwise, cross-session comparisons can be misleading. For this reason, many athletes use a benchmark like Functional Threshold Power (FTP) to set training zones and track improvements over time.

In practice, a watt plan helps you quantify training load without relying solely on cardio signals. A typical session might alternate between steady-state blocks at a set watt and short, high-intensity intervals that spike power outputs. The clarity of watts makes it easier to translate a workout into measurable gains, whether you are cycling, using a rowing machine with a power function, or engaging in resistance-based ergometry that reports power output.

Practical tip: start with a baseline watt target that matches your fitness level, then adjust by 5–10% every 1–2 weeks if your machine and test protocol remain consistent. Keep the same equipment for longitudinal tracking, and document any calibration changes that might affect readings.

What are METs and why they matter?

MET stands for metabolic equivalent. By definition, 1 MET equals the energy cost of sitting quietly, roughly 3.5 mL of oxygen per kilogram of body weight per minute. MET values provide a standardized way to gauge exercise intensity across activities, independent of body weight or specific equipment. Activities are categorized by typical MET ranges; for example, walking at a comfortable pace may be around 3–4 METs, while running can span roughly 6–12 METs depending on speed and incline. On many machines, METs are displayed to help users estimate intensity when exact power data isn’t available.

The value of METs lies in cross-activity comparability. If you train across different modalities—treadmill, stationary bike, elliptical, or rowing—METs allow you to translate effort into a common metric. This is especially useful for general programming, for populations with different training histories, or when comparing workouts done with varying equipment. However, it is important to recognize that MET values are estimations and rest on standard assumptions about body mass and oxygen cost; individual variations in efficiency, body composition, and conditioning can shift the actual energy cost.

Understanding METs helps you plan workouts when watts aren’t accessible. For example, a treadmill session at 6 METs generally represents a brisk but sustainable effort, while cycling at 6–8 METs might require stronger legs and higher conditioning. For trainers, METs offer a practical language for prescribing intensity in mixed routines and for estimating caloric expenditure using a simple formula: calories per minute ≈ MET × body weight in kg × 0.0175.

Limitations of METs include their reliance on standard body parameters and linear approximations of energy cost. They may overestimate energy expenditure for some individuals (e.g., those with higher efficiency or unique biomechanics) and underestimate for others (e.g., untrained populations or those with joint limitations). Always use METs as a guide alongside other measures such as heart rate, RPE, and power when possible.

Practical Application: Using Watts and METs in Training

How to read watts on different machines

On cycling and resistance machines, watts are a direct readout showing the instantaneous power output. Stationary bikes, smart bikes, and many modern rowers report watts when a power meter is integrated. Elliptical trainers sometimes display power as wattage, but many models emphasize pace, resistance, and calories, with watts available primarily on higher-end or connected machines. When a machine reports watts, use it as the primary driver of intensity during interval work and steady-state blocks. If your machine does not display watts, you can approximate effort using pace, incline, and perceived exertion, then translate that effort into a comparable watt target when possible.

Interpreting numbers requires context. For a well-trained cyclist, 200–250 W might feel moderate during a 60-minute session, while a novice might find 150 W quite challenging. A practical approach is to establish a starting watt target based on FTP or a 20-minute test, then adjust in small increments as you collect data. When you switch machines, recalibrate and re-establish your targets to avoid drift in intensity. Documentation of equipment, test protocol, and environmental factors (temperature, humidity) supports accurate longitudinal tracking.

Establish a simple framework to set targets: Step 1, determine a baseline watt value from a recent test. Step 2, choose training zones defined as a percentage of FTP (for example, Zone 2 at ~56–75% of FTP, Zone 3 at ~76–90%). Step 3, structure sessions with blocks of 5–15 minutes at the target watt, interspersed with recovery. Step 4, log watts, duration, and subjective effort to observe progression over weeks and months.

Real-world example: a 75 kg rider with an FTP of 180 W trains to Zone 2 (roughly 101–135 W) for two 12-minute blocks on a mid-range indoor bike. They complete a 5-minute warm-up at 60–70 W and a 5-minute cooldown, totaling 40 minutes. Over several weeks, they notice an increase in the average watt of Zone 2 without a rise in perceived exertion, indicating improved efficiency and endurance.

How METs translate to workouts and populations

MET-based planning helps when you lack a power meter or are incorporating multiple modalities. For example, a 6 MET run, a 4–5 MET bike ride, and a 3–4 MET walk all reflect a moderate to vigorous effort relative to rest. For older adults or beginners, staying within 3–5 METs during most workouts reduces injury risk while still delivering meaningful training stimulus. For athletes, pushing into 6–8 METs during intervals can elicit higher cardio adaptation and VO2max improvements. When you combine METs with power data, you gain a rich picture of both relative intensity and absolute load.

To estimate calories, use the formula calories per minute ≈ MET × body weight (kg) × 0.0175. For a 70 kg person exercising at 6 METs, this equals about 7.7 kcal per minute, or roughly 462 kcal per hour. This calculation is a guideline; actual energy expenditure varies with efficiency, biomechanics, and environmental factors. When possible, corroborate MET estimates with heart rate zones and rate of perceived exertion (RPE) to ensure the session aligns with your goals.

Practical tip: use MET targets to plan mixed workouts that include intervals across activities. For instance, a 40-minute session could feature 10 minutes at 4 METs (easy), 8 minutes at 6 METs (moderate-to-vigorous), and 6 minutes at 5 METs (steady), repeated as needed. Always consider the individual’s conditioning status and medical history when prescribing MET-based workloads.

Limitations in MET readings include dependency on standard body mass assumptions and the generalization of energy cost. Machine-derived METs may not perfectly reflect your personal energy expenditure, especially if you have unique biomechanics or carry extra body weight. Use METs as a practical guide rather than an exact measurement, and prefer power metrics when available for precise dose control.

Practical Application Guide: Summary and Best Practices

• Consistency matters: use the same machine, test protocol, and environment for trend data.
• Combine metrics: use watts for dose control and METs for cross-activity comparisons.
• Set progressive targets: adjust watts or METs by small increments every 1–3 weeks based on data.
• Monitor recovery: if you consistently exceed intended zones, incorporate longer rest or easier sessions to avoid overreaching.
• Document calibration: track device calibration and firmware updates that may affect readings.

Frequently Asked Questions

Introduction: Watts and METs are powerful tools for quantifying exercise intensity, yet they serve different purposes. This FAQ clarifies common questions to help you apply these metrics effectively across workouts and equipment.

• Q: What is the main difference between watts and METs? A: Watts measure instantaneous power output on a machine, reflecting how hard you are pushing against resistance. METs estimate energy cost relative to rest; they provide cross-activity intensity comparisons and caloric estimates.
• Q: Do all fitness machines show watts?
A: No. Some machines display watts, especially bikes and rowers with power meters. Others show pace, resistance, or calories, and you may need an external power meter for precise watt readings.
• Q: How do I determine my FTP for watts-based training?
A: FTP is typically established via a standardized test (e.g., 20-minute all-out effort) and represents your sustainable peak power. Use 95% of the average 20-minute power as a practical FTP estimate, then define training zones from there.
• Q: Can METs be used to prescribe workouts without a power meter?
A: Yes. METs help categorize intensity across activities. Use treadmill, bike, or cross-training MET values to structure sessions with consistent effort, especially when a power meter isn’t available.
• Q: Are MET values accurate for everyone?
A: METs are estimates based on population norms. Individual energy cost varies due to body size, efficiency, training status, and health conditions, so use METs as guidance alongside other cues.
• Q: How do I convert watts to METs?
A: There is no direct universal conversion because watts reflect mechanical power and METs reflect metabolic cost. Both are useful; you may correlate training blocks by observing how changes in watts influence perceived effort and MET estimates.
• Q: What is considered light, moderate, and vigorous in MET terms?
A: Light activity is roughly 1.5–3 METs, moderate around 3–6 METs, and vigorous typically above 6 METs, though individual tolerance varies with conditioning and health status.
• Q: Can training with watts improve VO2 max?
A: High-intensity, power-based intervals and sustained power work can elicit cardio adaptations that raise VO2 max, especially when integrated with proper recovery and progression.
• Q: How should beginners start with watts and METs?
A: Begin with lower targets, focus on consistent sessions, use METs to ensure manageable effort, and progressively introduce higher watt work as fitness improves. Prioritize technique and safety.
• Q: How should I combine watts and METs in a weekly plan?
A: Use watts for dose control during intervals, and METs to shape longer steady-state workouts across mixed modalities. Alternate days between power-focused sessions and MET-driven cardio to balance load.
• Q: How do I calibrate my equipment for accurate readings?
A: Regularly calibrate the power meter according to manufacturer instructions, keep firmware up to date, and use the same device for tracking progress to maintain consistency.
• Q: Is a higher watt or MET value always better?
A: Not necessarily. Progression should align with your goals, current fitness, and recovery status. Focus on sustainable improvements rather than chasing higher numbers alone.