triathlon race time predictor
Triathlon Race Time Calculator & Predictor
Find your Ironman or 70.3 race, load available course profiles, and estimate your swim, bike and run splits. Or choose any distance from sprint to marathon. Try it free with your own fitness numbers — no signup needed.
How to use it
- 1
Search for your race or city to load available course profiles, or choose a generic distance. You can also upload a GPX.
- 2
Enter your FTP (watts) and body weight, and choose a road or TT/tri bike setup.
- 3
Enter your run threshold pace (your roughly one-hour race pace per km).
- 4
Enter your swim CSS (critical swim speed) per 100 m — use the CSS calculator if you don't know it.
- 5
Read your conservative/target/stretch finish, per-leg splits with target power and pace, and your estimated transitions.
Not another flat finish-time formula
Most predictors apply one Riegel exponent to a single input and hand you a single number. This runs the same model PaceBeats uses inside the app: the bike leg solves the aerodynamic drag and rolling-resistance equation for the speed your race power produces, the swim adds distance degradation plus an open-water wetsuit adjustment, and the run stacks a distance factor with a triathlon run-off fatigue multiplier — because a 70.3 half-marathon off the bike is nothing like an open half-marathon.
A range, not a false-precision number
Real races land in a window, so this gives you one: a conservative, target and stretch finish built from a confidence band, not a single time pretending to be exact. The width is driven by how much the model can trust your inputs — three solid thresholds tighten it, a missing one widens it — and each triathlon estimate folds in the transitions most calculators quietly ignore.
The product predictor, with honest cold-start defaults
The free calculator uses your typed thresholds and any loaded course profiles. Select a covered race to load its stored routes, or upload your own GPX. Stored routes may differ from your race edition, so check the organiser's latest information. After signup, connect Garmin and use My training data to calculate from saved fitness and available training history. Imports take time, and missing measurements remain estimates. Calculator inputs never overwrite your fitness profile.
Used as a 70.3 time calculator
The half distance is where a calculator earns its keep: long enough that pacing physics dominate, short enough that a realistic target changes how you race. For a 70.3 the model sets your bike power at about 75% of FTP — the sustained fraction pacing guidelines put on a half — solves for the speed that power buys on your setup, slows your open half-marathon pace with the run-off fatigue multiplier, and adds transitions. Three thresholds in, and you get a Half Ironman finish window you can build a pacing plan around.
Ironman and sprint: the fractions change, not the physics
The same model spans the whole sport by changing the sustainable fraction of your FTP: about 92% for a sprint, 87% for an Olympic, 75% for a 70.3 and 68% for a full Ironman. That is why a spreadsheet that doubles your 70.3 time misses badly — an Ironman is ridden at a lower fraction of your FTP, and the marathon leg stacks a bigger distance factor onto your threshold pace before the run-off fatigue is applied. The calculator races each distance on its own terms instead of scaling another distance's time.
Common questions
How accurate is the triathlon time predictor?
Accuracy depends on your inputs, available course data and race-day conditions. Loaded course profiles can account for elevation, but wind, heat, nutrition and pacing can still change your result. Typed thresholds are self-reported, not verified tests. Treat the estimate and pacing targets as planning aids, not guaranteed finish times.
Why does it show a range instead of one time?
Race outcomes are uncertain. The calculator shows a target with conservative and stretch pacing options, while its confidence assessment reflects the available evidence. Typed thresholds remain self-reported. Training history and measured fitness can add context after signup, but do not guarantee a narrower range or a faster prediction.
What's the difference between this and a Riegel calculator?
A Riegel calculator extrapolates one known time to another distance with a fixed exponent. This predictor models each discipline from your physiological thresholds and the physics of cycling, adds the triathlon-specific run-off fatigue and transitions a single-sport formula can't capture, and expresses the result as a calibrated range with a confidence tier.
How do I calculate my 70.3 (Half Ironman) time?
Pick Half Ironman (70.3) as the race, then enter your FTP and weight, your run threshold pace, and your swim CSS. The calculator sets your bike power at about 75% of FTP, solves for the speed that power produces on your bike setup, degrades your swim and run paces for the distance, adds run-off fatigue and transitions, and returns a conservative, target and stretch finish. A missing threshold doesn't stop it — the range just gets honestly wider.
Does it work as an Ironman time calculator?
Yes — sprint, Olympic, 70.3 and full Ironman, plus standalone runs from 5K to marathon. Each distance uses its own sustainable fraction of FTP (about 68% for a full Ironman against 92% for a sprint) and its own run-fatigue factors, so the full distance is modeled as its own race rather than as a doubled 70.3.
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