Triathlon Calculator | Sprint, Olympic, 70.3 & Ironman
Free triathlon calculator: estimate finish times from Sprint to Ironman using your swim CSS, bike FTP, and easy run pace. Includes pace calculator, split breakdown, and realistic time ranges.
Triathlon Calculator
Enter your swim, bike, and run fitness markers to get estimated finish times from Sprint to full Ironman — with realistic best-case to conservative ranges.
Your pace per 100m from a CSS test: (400m time − 200m time) / 2. Represents your threshold swim pace.
The highest average power you can sustain for ~1 hour. Typically measured via a 20-min test (95% of 20-min power).
Your comfortable conversational-pace run. Typically 1:00–1:30/km slower than marathon pace. This reveals your aerobic running fitness.
Enter your swim CSS, bike FTP, and easy run pace to see estimated triathlon finish times across all distances.
How CSS Predicts Swim Times
Critical Swim Speed (CSS) approximates your lactate threshold pace in the water — the fastest pace you can sustain aerobically. For a 1500m Olympic swim, your CSS is a strong predictor. For shorter sprints you'll swim faster; for Ironman's 3800m, fatigue and open-water factors add 8–12 seconds per 100m.
FTP and Race Intensity
Your FTP represents ~1 hour of maximum sustainable power. In a Sprint tri you can push 90–95% of FTP; in an Ironman, pacing at 68–76% is critical for a successful run off the bike. The calculator models power-to-speed using aerodynamic drag and rolling resistance for a flat course.
Easy Pace to Race Pace
Your easy (conversational) run pace reveals your aerobic engine. Using the Daniels VDOT model, we derive your VO2max equivalent and predict standalone race times. A triathlon-specific adjustment accounts for cumulative fatigue from swimming and cycling before the run.
Understanding the Range
The time range accounts for real-world variability: course profile (flat vs. hilly), weather, wetsuit legality, drafting rules, nutrition execution, and race-day form. The low end assumes favorable conditions and strong execution; the high end reflects conservative pacing or challenging conditions.
Frequently Asked Questions
For athletes with consistent training across all three disciplines, predictions typically fall within the displayed range. The model assumes a flat course at sea level. Hilly courses, altitude, heat, or poor nutrition can push times above the conservative estimate.
Swim a 400m time trial and a 200m time trial with full rest between. CSS pace = (400m time − 200m time) / 2, expressed as pace per 100m. For example: 400m in 6:20 and 200m in 2:50 gives CSS = (380 − 170) / 2 = 105s = 1:45/100m.
Yes. T1 (swim-to-bike) and T2 (bike-to-run) are included with typical ranges: T1 averages 2–4 minutes and T2 averages 1–3 minutes, depending on race distance and experience level.
Running a marathon after 180km of cycling and 3.8km of swimming is fundamentally different from a standalone marathon. The calculator applies a fatigue factor of 10–22% slowdown for Ironman, which matches real-world data from age-group finishers.