Free TSS Calculator - Training Stress Score for Cycling
Calculate Training Stress Score for your cycling workouts using power, duration, and FTP
What is Training Stress Score (TSS)?
Training Stress Score (TSS) quantifies the training load of a cycling workout by combining intensity and duration based on your power output. Developed by Dr. Andrew Coggan, TSS uses your Functional Threshold Power (FTP) as the reference point. A 1-hour workout at FTP = 100 TSS.
Free TSS Calculator
Calculate training stress for any cycling workout using power data.
How TSS is Calculated
TSS Formula
Where:
- NP (Normalized Power) = Physiological "cost" of the ride in watts
- IF (Intensity Factor) = NP / FTP (intensity relative to threshold)
- Duration = Total ride time in seconds
- FTP = Your Functional Threshold Power in watts
Simplified: TSS = Duration (hours) × IF² × 100
Worked Examples
Example 1: Easy Endurance Ride
Rider Data:
- FTP: 250W
- Duration: 120 minutes (7200s)
- Normalized Power: 150W
Step 1: Calculate Intensity Factor
IF = 150W / 250W
IF = 0.60
Step 2: Calculate TSS
TSS = (648,000) / (900,000) × 100
TSS = 72 TSS
Interpretation: Easy endurance ride at 60% intensity—perfect for aerobic base building and recovery.
Example 2: Threshold Intervals
Rider Data:
- FTP: 250W
- Duration: 90 minutes (5400s)
- Normalized Power: 235W
Step 1: Calculate Intensity Factor
IF = 235W / 250W
IF = 0.94
Step 2: Calculate TSS
TSS = (1,192,860) / (900,000) × 100
TSS = 133 TSS
Interpretation: Hard threshold session at 94% intensity—significant training stimulus for FTP improvement.
Example 3: Hard Group Ride
Rider Data:
- FTP: 250W
- Duration: 180 minutes (10800s)
- Normalized Power: 210W
Step 1: Calculate Intensity Factor
IF = 210W / 250W
IF = 0.84
Step 2: Calculate TSS
TSS = (1,905,120) / (900,000) × 100
TSS = 212 TSS
Interpretation: Long hard ride at 84% intensity—high training load requiring 1-2 days recovery.
Example 4: VO₂max Intervals
Rider Data:
- FTP: 250W
- Duration: 75 minutes (4500s)
- Normalized Power: 270W
Step 1: Calculate Intensity Factor
IF = 270W / 250W
IF = 1.08
Step 2: Calculate TSS
TSS = (1,312,200) / (900,000) × 100
TSS = 146 TSS
Interpretation: Very hard VO₂max session above threshold—high training stimulus despite shorter duration.
TSS Guidelines by Workout Type
| Workout Type | TSS Range | Intensity Factor | Description |
|---|---|---|---|
| Recovery Ride | 20-50 TSS | IF < 0.65 | Easy spinning, 30-60 minutes |
| Easy Endurance | 50-100 TSS | IF 0.65-0.75 | Conversational pace, 1-2 hours |
| Moderate Endurance | 100-150 TSS | IF 0.75-0.85 | Steady riding, 2-3 hours |
| Tempo Ride | 150-200 TSS | IF 0.85-0.95 | Sweet spot, tempo work, 2-3 hours |
| Threshold Workout | 200-300 TSS | IF 0.95-1.05 | FTP intervals, race sim, 2-4 hours |
| VO₂max Intervals | 150-250 TSS | IF 1.05-1.15 | Hard intervals, 1-2 hours high intensity |
| Race/Hard Event | 200-400 TSS | IF 0.90-1.05 | Criteriums, road races, 2-5 hours |
Weekly TSS Targets by Cyclist Level
Beginner Cyclists
Weekly TSS: 200-400
3-4 rides per week, 50-100 TSS each. Focus on building aerobic base and bike handling skills.
Recreational Cyclists
Weekly TSS: 400-600
4-5 rides per week, 80-120 TSS each. Mix of endurance and some quality sessions.
Competitive Amateurs
Weekly TSS: 600-900
5-7 rides per week, 85-130 TSS each. Structured training with periodization and racing.
Elite / Professional
Weekly TSS: 900-1500+
10-15+ sessions per week. High volume professional training load. Post-Grand Tour CTL: 150-170.
⚠️ Important Notes About TSS
- Requires accurate FTP: Your FTP must be current (tested within 4-6 weeks) for accurate TSS.
- Use Normalized Power, not Average Power: NP accounts for variability and physiological cost.
- Indoor vs Outdoor: Indoor TSS may feel harder due to no coasting or descents.
- Individual variation: Same TSS feels different for different riders. Adjust based on your recovery.
- Ramp rate matters: Increase weekly TSS gradually—3-8 CTL points per week is sustainable.
Understanding Normalized Power (NP)
Normalized Power is more accurate than Average Power for calculating TSS because it accounts for the physiological cost of power variability:
Why NP Matters: Two Rides Compared
Ride A: Steady Tempo
- Duration: 60 minutes
- Average Power: 200W
- Normalized Power: 202W
- Variability Index: 1.01
- TSS: 65
Steady, consistent effort—low physiological cost
Ride B: Hard Group Ride
- Duration: 60 minutes
- Average Power: 200W
- Normalized Power: 240W
- Variability Index: 1.20
- TSS: 92
Variable with surges—much higher physiological cost
Key insight: Both rides have 200W average, but Ride B is 42% harder (92 vs 65 TSS) due to power variability. NP captures this difference.
💡 How to Get Normalized Power
Most cycling computers and apps calculate NP automatically:
- Garmin/Wahoo/Hammerhead: Shows NP in ride summary
- TrainingPeaks/Strava/Intervals.icu: Calculates NP from uploaded rides
- Golden Cheetah/WKO5: Advanced NP analysis tools
If you only have average power, estimate: NP ≈ Average Power × 1.03-1.05 for steady rides, × 1.10-1.15 for variable rides.
Why TSS Matters: CTL, ATL, TSB
Training Stress Score is the foundation for the Performance Management Chart:
- CTL (Chronic Training Load): Your fitness level - 42-day exponentially weighted average of daily TSS
- ATL (Acute Training Load): Your fatigue - 7-day exponentially weighted average of daily TSS
- TSB (Training Stress Balance): Your form - TSB = CTL - ATL (positive = fresh, negative = fatigued)
- Periodization: Plan training phases (base, build, peak, taper) using target CTL progressions
- Race Timing: Taper to achieve TSB of +10 to +25 on race day for peak performance
Pro Tip: Track Your Performance Management Chart
Log daily TSS in TrainingPeaks, Intervals.icu, or a spreadsheet. Monitor your CTL (42-day average) and ATL (7-day average). Target steady CTL growth of 3-8 points per week during base building. Reduce TSS 7-14 days before races to let TSB rise to positive values for peak performance.
Frequently Asked Questions
What if I don't have a power meter?
TSS requires power data (FTP and Normalized Power). Without a power meter, you can use heart rate-based alternatives like HRSS (Heart Rate Stress Score) or use perceived exertion estimates, but these are less accurate. Power meters are the gold standard for TSS calculation and training load management in cycling.
How accurate is TSS?
TSS is highly accurate when based on current FTP and properly calculated Normalized Power. Studies show TSS reliably predicts training load and recovery needs. Accuracy depends on: recent FTP test (within 4-6 weeks), correct NP calculation, and power meter accuracy (most are ±1-2%).
Can I compare TSS between road and MTB?
Yes, but with caveats. Road cycling TSS is more predictable with steady power profiles (VI 1.02-1.05). MTB TSS is highly variable (VI 1.10-1.20+) with frequent bursts above threshold. Same TSS from MTB may feel harder due to technical demands. Focus on trend analysis rather than absolute comparisons between disciplines.
What's a good TSS for one workout?
It depends on training goals: Recovery rides: 20-50 TSS, Easy endurance: 50-100 TSS, Moderate rides: 100-150 TSS, Hard workouts: 150-250 TSS, Very hard sessions/races: 200-400+ TSS. Most training rides fall between 50-150 TSS. Quality intervals generate 100-200 TSS. Racing and long events: 200-400+ TSS.
How much TSS should I do per week?
Weekly TSS targets by level: Beginners: 200-400 TSS/week, Recreational: 400-600 TSS/week, Competitive amateur: 600-900 TSS/week, Elite/Professional: 900-1500+ TSS/week. Start conservatively and increase by 3-8 CTL points per week. Your sustainable weekly TSS depends on training history, available time, and recovery ability.
Should I use TSS for indoor training?
Absolutely. TSS is ideal for indoor training because power is consistent and there are no environmental variables. Indoor TSS directly contributes to your CTL/ATL/TSB. However, indoor rides may feel harder than outdoor for the same TSS due to no coasting, descents, or wind-assisted sections.
What's the difference between TSS and kilojoules?
Kilojoules measure total work done (energy expenditure)—same for everyone at the same power. TSS measures training stress relative to YOUR FTP. Example: 200W for 1 hour = 720 kJ for everyone. But if your FTP is 200W, TSS = 100. If your FTP is 300W, TSS = 44. TSS is individualized; kJ is absolute.
Do I need to know my FTP?
Yes, FTP is essential for TSS calculation. Without knowing your FTP, you cannot calculate Intensity Factor or TSS. Test your FTP using a 20-minute or 8-minute test, or use Ramp Test protocols. Retest every 4-6 weeks to keep TSS calculations accurate as your fitness improves. Learn more: FTP Testing Guide
Related Resources
FTP Testing
Need your FTP? Learn how to test Functional Threshold Power accurately.
FTP Guide →Training Load Guide
Learn about CTL, ATL, TSB and Performance Management Chart metrics.
Training Load →Power Metrics
Understand Normalized Power, Intensity Factor, and Variability Index.
Power Metrics →Want automatic TSS tracking with CTL/ATL/TSB charts?
Learn About Bike Analytics