Duathlon Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Result
Enter a pace or speed for each leg to see your finish time and splits.
Estimate only — real results depend on course, weather, terrain, fatigue, transitions, equipment, nutrition and event rules. Not medical or coaching advice.
How to use this calculator
- Pick Sprint, Standard or Custom.
- Enter your run 1 pace, bike speed, run 2 pace and the T1/T2 transitions.
- Read your total time and splits, or use Target Finish to solve a required pace/speed.
How it works
A duathlon is run → bike → run. Each run = distance × pace per km, the bike = (distance ÷ speed) × 3600, and transitions are added. The total is the sum of all five legs.
Worked example
Sprint duathlon. 5 km run @ 5:00/km (25:00), 20 km bike @ 32 km/h (37:30), 2.5 km run @ 5:30/km (13:45), plus transitions.
Tips
- Times are estimates only — not medical or coaching advice. Always train safely and follow event rules.
- Distances are editable: choose “Custom…” to enter your own course lengths.
Frequently asked questions
What are typical duathlon distances?
Sprint ≈ 5 km run / 20 km bike / 2.5 km run; Standard ≈ 10 km run / 40 km bike / 5 km run. Courses vary, so distances are editable.
How accurate are these times?
They're estimates. Real race times depend on terrain, weather, elevation, fatigue, transitions, nutrition, equipment, drafting and water conditions. Use them for planning and pacing, not as a guarantee.
Do my inputs get uploaded?
No. Everything is calculated in your browser — nothing is sent to a server or stored.
What is Target Finish mode?
Enter a goal finish time and the paces/speeds for the other legs, then pick the leg to ‘solve for’. The calculator works out the pace or speed you'd need on that leg to hit your goal.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.