Duathlon Calculator
Use this duathlon calculator to plan your run-bike-run race. Duathlons replace the swim with a second run — typically a 5km run, 20km bike, 2.5km run for sprint or 10km run, 40km bike, 5km run for standard. Enter your run pace and bike speed to get your projected finish. Set the swim distance to 0 in the calculator above, then enter your first run, bike, and second run paces.
Race distance
Pace & transitions
Results
Duathlon Calculator for Run-Bike-Run Splits
Use this duathlon calculator for run-bike-run pacing. A duathlon needs a different pacing model from a triathlon because there is no swim: the race starts with running, moves to cycling, and finishes with a second run.
The calculator above uses the triathlon engine with the swim set to zero. Enter your first run pace using the run fields, your bike speed in the bike fields, and use the notes below to model the second run. For exact second-run modeling, use the custom fields and compare scenarios, or treat the run field as the combined running distance with an average pace that accounts for fatigue.
Duathlon pacing is easy to get wrong because the first run feels familiar. If you race it like an open 5K or 10K, the bike power usually drops and the second run becomes survival. A better plan is to run the first leg controlled, ride steadily, then use cadence and form to manage the final run.
How to Model Run-Bike-Run Pacing
Because the current calculator uses one run field, the cleanest approach is to enter the combined run distance and use an average run pace that reflects both run legs. Then use the example splits below to sanity-check the opening and closing run separately.
Do not let the first run dominate the plan. A first run that is 30 seconds per kilometer too fast can make the bike feel flat and the second run much slower. Controlled early running is usually the fastest total strategy.
For custom duathlon formats, set the swim distance to zero, enter the official bike course, and adjust transitions to match your race layout. Short duathlons reward clean transitions almost as much as raw running speed.
Duathlon Split Examples
Sprint duathlon
- Run 1 at 4:30/km for 22:30
- Bike 33 km/h for about 36:20
- Run 2 at 4:45/km for about 11:50
- Transitions total 1:30
Projected finish: about 1:12:10
Standard duathlon
- Run 1 at 5:00/km for 50:00
- Bike 32 km/h for 1:15:00
- Run 2 at 5:15/km for 26:15
- Transitions total 2:00
Projected finish: about 2:33:15
Duathlon Pacing Tips
Keep the first run slightly easier than open-race pace. The goal is to arrive at the bike with rhythm, not damage.
Bike smoothly and avoid big surges. The second run starts with already-loaded legs, so spiky power is expensive.
Practice mounting, dismounting, and shoe changes. Duathlon transitions are short, and small errors cost a meaningful percentage of total time.
Duathlon Run-Bike-Run Planning Answers
These answers adapt the planning framework for duathlon: first-run restraint, bike split estimates, second-run fatigue, and transition execution without a swim leg.
Use this page to model sprint, standard, or custom run-bike-run races.
How to Use the Duathlon Calculator
Use this calculator for run-bike-run planning when there is no swim leg. Set the swim distance to zero, enter the bike course, and model the running with either a combined run pace or separate examples for the first and second run.
The main mistake in duathlon is treating the first run like an open running race. A controlled first run often produces a faster total result because the second run is where overpacing becomes visible.
For sprint and standard duathlons, pay close attention to transitions and second-run fatigue. A clean setup and a patient first run can save more time than forcing a bike split you cannot run from.
Frequently Asked Questions
What is a duathlon?
A duathlon is a run-bike-run multisport race. It replaces the swim leg of a triathlon with an opening run.
What are common duathlon distances?
Common formats include 5 km run, 20 km bike, 2.5 km run for sprint and 10 km run, 40 km bike, 5 km run for standard.
How do I use this calculator for duathlon?
Set swim to zero, enter the bike distance and speed, and model the running distance using your combined or target run pace.
How hard should the first run be?
Usually controlled, around 85-90% effort. Running too hard early often costs more time on the bike and second run.
Is duathlon harder than triathlon?
It depends on the athlete. Strong swimmers may find duathlon harder because the second run creates heavy leg fatigue.
Can I calculate a custom duathlon format?
Yes. Use custom distances to match local races, off-road events, or long-course duathlons.
Assumptions & Limitations
The estimates on this page are planning tools, not race guarantees. Your actual finish time depends on course profile, weather, water conditions, drafting rules, equipment, nutrition, heat, elevation, training history, and how well you pace each discipline on race day.
Swim pace estimates assume calm open water or pool conditions. Bike speed estimates assume flat terrain with minimal wind unless adjusted manually. Run pace estimates assume a flat course with moderate temperatures. Transitions vary significantly by venue layout, race size, and personal preparation.
Always test your pacing plan in training before race day. Use this calculator to compare scenarios, not to predict exact outcomes.
Sources & Methodology
The pacing benchmarks, wetsuit legality thresholds, TSS calculations, and FTP guidelines on this page are based on established sports-science principles and common age-group coaching practice:
- Swim drag reduction (18-26%): Reported draft effect ranges from open-water studies and computational fluid dynamics (CFD) modeling. Related research on PubMed. Actual savings depend on swimmer position, water conditions, and duration spent in drafting position.
- Wetsuit time savings (5-12 s/100m):Based on buoyancy and drag-reduction research in controlled pool and open-water settings. Related research on PubMed. Individual results vary by wetsuit fit, body composition, and swim technique.
- Carbon-plate shoe economy (2-4%):Published in peer-reviewed running-economy studies on super-shoe technology. Related research on PubMed. Benefits depend on shoe model, runner biomechanics, pace, and fatigue level.
- FTP pacing ranges: Based on age-group coaching recommendations from sources including TrainingPeaks coaching education, Joe Friel's "The Triathlete's Training Bible," and USAT-certified coaching guidelines.
- Carb intake targets (60-100 g/hr):Reflect current sports-nutrition consensus from the ISSN position stand and ACSM position stand on endurance fueling. Individual tolerance varies.
- TSS estimates: Use the standard Training Stress Score formula (TSS explained by TrainingPeaks). Run TSS is estimated using an analogous model. Actual TSS depends on power or pace data from your specific device.
These sources are cited as general references. The calculator does not account for every variable that affects race-day performance. Always consult a certified coach or sports-medicine professional for individualised pacing and nutrition plans.