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).
Frequently Asked Questions
What is Swimming TSS (sTSS)?
Swimming Training Stress Score (sTSS) is a metric that quantifies the training load of a swimming workout by combining both intensity and duration. It's adapted from cycling's TSS methodology, using your Critical Swim Speed (CSS) as the threshold pace. A workout of 1 hour at CSS pace equals 100 sTSS.
How do I calculate my sTSS?
Use the calculator above by entering your CSS pace (from a CSS test), total workout duration, and average pace during the workout. The formula is: sTSS = Duration (hours) × Intensity Factor² × 100, where Intensity Factor = CSS Pace / Average Workout Pace.
Do I need CSS to calculate sTSS?
Yes, your Critical Swim Speed (CSS) is required to calculate the Intensity Factor, which is essential for sTSS calculation. CSS represents your threshold pace and should be tested every 6-8 weeks. You can find your CSS using our CSS calculator.
What's a good sTSS score for one workout?
It depends on workout intensity: Easy workouts typically score below 50 sTSS, moderate workouts 50-100 sTSS, hard workouts 100-200 sTSS, and very hard workouts above 200 sTSS. The appropriate score depends on your training goals and current fitness level.
How much sTSS should I do per week?
Weekly sTSS targets vary by level: Recreational swimmers: 150-300, Fitness swimmers/Triathletes: 300-500, Competitive Masters: 500-800, Elite/Collegiate: 800-1200+. Start conservatively and increase gradually to avoid overtraining.
Is swimming TSS the same as cycling TSS?
The concept and formula are the same, but sTSS is adapted for swimming. Instead of using power (FTP) like cycling TSS, sTSS uses pace with CSS as the threshold. Both measure training load using Duration × Intensity Factor² × 100.
Can I use sTSS for all swim strokes?
Yes, but your CSS should be stroke-specific. Most swimmers use freestyle CSS since it's the most commonly trained stroke. If you train primarily in another stroke, perform a CSS test in that stroke and use that pace for sTSS calculation.
What's the difference between sTSS and CTL/ATL/TSB?
sTSS measures a single workout's training load. CTL (Chronic Training Load) is your long-term fitness, ATL (Acute Training Load) is your recent fatigue, and TSB (Training Stress Balance) is your freshness. These metrics use sTSS values over time to track your training state. Learn more in our Training Load guide.
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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