Free Swimming TSS Calculator
Calculate Training Stress Score for swimming workouts - The only free sTSS calculator
What is Swimming TSS (sTSS)?
Swimming Training Stress Score (sTSS) quantifies the training load of a swimming workout by combining intensity and duration. It's adapted from cycling's TSS methodology, using your Critical Swim Speed (CSS) as the threshold pace. A 1-hour workout at CSS pace = 100 sTSS.
Free sTSS Calculator
Calculate training stress for any swimming workout. Requires your CSS pace.
How sTSS is Calculated
Formula
Where:
- Intensity Factor (IF) = CSS Pace / Average Workout Pace
- Duration = Total workout time in hours
- CSS Pace = Your threshold pace from CSS test
Worked Example
Workout Details:
- CSS Pace: 1:49/100m (109 seconds)
- Workout Duration: 60 minutes (1 hour)
- Average Pace: 2:05/100m (125 seconds)
Step 1: Calculate Intensity Factor
IF = 109 / 125
IF = 0.872
Step 2: Calculate sTSS
sTSS = 1.0 × 0.760 × 100
sTSS = 76
Interpretation: This 60-minute workout at easy pace (slower than CSS) generated 76 sTSS - a moderate training load suitable for aerobic base building.
Understanding sTSS Values
| sTSS Range | Training Load | Recovery Time | Example Workout |
|---|---|---|---|
| < 50 | Low | Same day | Easy 30-min swim, technique drills |
| 50-100 | Moderate | 1 day | 60-min endurance, steady pace |
| 100-200 | High | 1-2 days | 90-min threshold sets, race pace intervals |
| 200-300 | Very High | 2-3 days | 2-hour hard training, multiple threshold blocks |
| > 300 | Extreme | 3+ days | Long race (>2 hours), ultra-endurance |
Weekly sTSS Guidelines
Target weekly sTSS depends on your training level and goals:
Recreational Swimmers
Weekly sTSS: 150-300
2-3 workouts per week, 50-100 sTSS each. Focus on technique and building aerobic base.
Fitness Swimmers / Triathletes
Weekly sTSS: 300-500
3-4 workouts per week, 75-125 sTSS each. Mix of aerobic endurance and threshold work.
Competitive Masters Swimmers
Weekly sTSS: 500-800
4-6 workouts per week, 80-150 sTSS each. Structured training with periodization.
Elite / Collegiate Swimmers
Weekly sTSS: 800-1200+
8-12 workouts per week, double days. High volume with recovery management critical.
⚠️ Important Notes
- Requires accurate CSS: Your CSS must be current (tested within 6-8 weeks) for accurate sTSS.
- Simplified calculation: This calculator uses average pace. Advanced sTSS uses Normalized Graded Pace (NGP) which accounts for interval structure.
- Not for technique work: sTSS only measures physical training stress, not skill development.
- Individual variation: Same sTSS feels different for different swimmers. Adjust guidelines based on your recovery.
Why sTSS Matters
Training Stress Score is the foundation for:
- CTL (Chronic Training Load): Your fitness level - 42-day exponentially weighted average of daily sTSS
- ATL (Acute Training Load): Your fatigue - 7-day exponentially weighted average of daily sTSS
- 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
- Recovery Management: Know when to push and when to rest based on TSB
Pro Tip: Track Your CTL
Record daily sTSS in a spreadsheet or training log. Calculate your 42-day average (CTL) weekly. Target 5-10 CTL points increase per week during base building. Maintain or slightly reduce CTL during taper (1-2 weeks before race).
Related Resources
CSS Test
Need your CSS pace? Use our free CSS calculator with 400m and 200m test times.
CSS Calculator →Training Load Guide
Learn about CTL, ATL, TSB and Performance Management Chart metrics.
Training Load →SwimAnalytics App
Automatic sTSS calculation for all workouts. Track CTL/ATL/TSB trends over time.
Learn More →Want automatic sTSS tracking?
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