Watts
Watts (Power)
Watts measure power output in cycling—how hard you're working at any moment. Learn what watts mean, how they're measured, and why power matters for cycling training.
Quick Answer
Watts — (W) measure power output in cycling—the rate at which work is done. One watt equals one joule of energy per second. Power meters measure watts directly, providing objective, instant feedback on how hard you're riding.
What Do Watts Mean in Cycling?
Power, measured in watts, tells you exactly how hard you're working at any moment. Unlike heart rate (which reacts slowly and varies with conditions), power is:
- Objective – Not affected by fatigue, heat, or caffeine
- Instant – Shows effort in real-time
- Reproducible – 200W today = 200W tomorrow
The physics definition:
Power (Watts) = Force × Velocity
Or more practically for cycling:
Power (Watts) = Work done (Joules) ÷ Time (seconds)
Use our Power to Speed Calculator to see how watts translate to speed.
Why Watts Matter
| Advantage | Why It Matters |
|---|---|
| Precision | Know exactly how hard you're working |
| Consistency | Compare efforts across different conditions |
| Pacing | Target specific power for races and workouts |
| Training zones | All zones based on power |
| Progress tracking | Objective fitness measurement |
Power transformed cycling training by removing guesswork from intensity prescription.
How Watts are Measured
Power meters use strain gauges to measure force and calculate power:
| Location | Type | Pros | Cons |
|---|---|---|---|
| Pedals | Pedal-based | Easy install, transferable | Cost, battery life |
| Cranks | Crank arm/spider | Accurate, durable | Requires installation |
| Hub | Rear hub | Works on any bike | Heavy, not transferable |
| Trainer | Smart trainer | Indoor training | Indoor only |
See our guide on Power Meters for detailed comparisons.
What's a Good Wattage?
Raw watts don't tell the whole story—body weight matters. See Watts Per Kg for relative comparisons.
Absolute Power Benchmarks
| Cyclist Type | Typical FTP (Watts) |
|---|---|
| Beginner | 100-180W |
| Recreational | 150-250W |
| Enthusiast | 200-280W |
| Competitive amateur | 250-320W |
| Elite amateur | 300-380W |
| Professional | 350-450W |
| WorldTour sprinter | 400-500W |
Use our FTP Calculator to find your threshold power.
Watts vs Heart Rate
| Factor | Power (Watts) | Heart Rate |
|---|---|---|
| Response time | Instant | 30-60 second lag |
| Affected by heat | No | Yes (rises) |
| Affected by caffeine | No | Yes (rises) |
| Affected by fatigue | Shows true output | May be elevated or suppressed |
| Indoor/outdoor | Consistent | Often higher indoors |
| Cost | Higher | Lower |
Power is the gold standard for intensity measurement, but heart rate remains useful for:
- Detecting fatigue (same watts, higher HR)
- Aerobic zone training without power meter
- Recovery monitoring
Understanding Power Duration
Your sustainable power decreases with duration:
| Duration | % of Max | Example (300W FTP) |
|---|---|---|
| 5 seconds | 300-400% | 900-1200W |
| 30 seconds | 150-200% | 450-600W |
| 1 minute | 130-150% | 390-450W |
| 5 minutes | 110-125% | 330-375W |
| 20 minutes | 103-108% | 310-325W |
| 60 minutes | 100% | 300W (FTP) |
This relationship forms your "power curve" or "power profile."
Power Calculations
Power to Speed
Power determines speed through several factors:
Speed = f(Power, CdA, Weight, Gradient, Rolling Resistance)
Try our Power to Speed Calculator to model different scenarios.
Calories from Power
Power provides accurate calorie calculation:
Calories = (Watts × Duration in hours × 3600) / 4184 / Efficiency
Where efficiency is typically 20-25%. Use our Cycling Calorie Calculator.
Training with Power
Zone-Based Training
All training zones derive from FTP:
| Zone | % of FTP | Power (250W FTP) |
|---|---|---|
| Zone 1 | < 55% | < 137W |
| Zone 2 | 56-75% | 140-187W |
| Zone 3 | 76-90% | 190-225W |
| Zone 4 | 91-105% | 228-262W |
| Zone 5 | 106-120% | 265-300W |
| Zone 6 | 121-150% | 302-375W |
Use our Training Zone Calculator.
Workout Examples
| Workout | Target Power |
|---|---|
| Easy recovery | < 55% FTP |
| Endurance base | 56-75% FTP |
| Sweet spot intervals | 88-94% FTP |
| Threshold intervals | 95-105% FTP |
| VO2 Max intervals | 106-120% FTP |
Common Questions
How do I increase my watts?
Structured training increases sustainable power:
- Build aerobic base (Zone 2)
- Sweet spot training (88-94% FTP)
- Threshold intervals (95-105% FTP)
- VO2 Max work (106-120% FTP)
See How to Improve FTP.
What watts do I need for races?
It depends on the race type:
- Flat criterium: High absolute watts for sprints
- Hilly road race: High W/kg for climbs
- Time trial: Sustained threshold power
Why are my watts lower than expected?
Common causes:
- Fatigue or poor recovery
- Heat or dehydration
- Power meter calibration needed
- FTP set too high
- Illness or life stress
Are left/right power meters necessary?
Single-sided meters (doubling one leg) are typically within 2-3% of dual-sided for most cyclists. Dual-sided helps identify imbalances but isn't essential for training.