Triathlon Calculator

About the Triathlon Calculator

A triathlon combines swimming, cycling and running in one continuous race, with transitions between them. Your finish time is the sum of five parts: the swim, the first transition (T1), the bike, the second transition (T2) and the run. Predicting it helps you set a realistic goal, plan pacing, choose a start wave and see where training will save the most time.

This triathlon calculator predicts a finish time from your swim pace per 100 metres, average bike speed and run pace per kilometre, plus transition times. Choose sprint, Olympic, half (70.3) or full (Ironman) distance to fill in the standard distances, or enter your own. It shows the split for each leg, each leg's share of the race and the equivalent paces.

How to Use the Triathlon Calculator

Choose the race distance, or adjust the swim, bike and run distances.

Enter your swim pace per 100 m and run pace per km as minutes and seconds.

Enter your bike speed in km/h and the T1 and T2 times in minutes.

The Formulas

  swim   = swim distance (m) ÷ 100 × pace per 100 m
  bike   = bike distance (km) ÷ speed (km/h)
  run    = run distance (km) × pace per km
  total  = swim + T1 + bike + T2 + run

Step-by-Step Example

An Olympic distance race: 1.5 km at 2:00 per 100 m, 40 km at 30 km/h, 10 km at 5:30 per km, T1 3 minutes, T2 2 minutes.

  swim    15 × 2:00 = 30:00
  bike    40 ÷ 30 = 1:20:00
  run     10 × 5:30 = 55:00
  T1+T2   5:00
  total   2:50:00

The bike is 47% of the race, the run 32%, the swim 18% and transitions 3%.

Standard Distances

Sprint races are 750 m swim, 20 km bike and 5 km run, a good first triathlon. Olympic or standard distance doubles that: 1.5 km, 40 km and 10 km. Half Ironman or 70.3 races cover 1.9 km, 90 km and 21.1 km, totalling 70.3 miles. A full Ironman is 3.8 km, 180 km and a full 42.2 km marathon. Local races sometimes vary the distances, so check the course details.

Where the Time Goes

The bike usually takes the biggest share of the race, roughly half at most distances, so even small improvements in bike speed save many minutes. The swim is the shortest part, but a poor swim can leave you tired for the rest of the race. The run comes last, on tired legs, so pacing the bike sensibly often produces a faster overall time than riding as hard as possible.

Race-Day Adjustments

Training paces rarely transfer directly. Open-water swimming involves sighting, waves and crowds, so it is often slower than pool pace, although a wetsuit can make you faster. Bike speed depends heavily on hills, wind and road surface. Running after cycling feels very different from a fresh run. Many athletes add 5 to 10% to their pool and solo-run paces when predicting a race.

Transitions

Transitions are free time to gain. A smooth T1 includes running from the water, removing a wetsuit, putting on a helmet and running the bike to the mount line; a smooth T2 is racking the bike and changing shoes. Practising them, using elastic laces and laying out kit neatly can save minutes compared with a chaotic changeover.

Training Priorities

Use the splits to decide where to focus. If the bike is your slowest discipline relative to others, extra cycling often gives the biggest return. Brick workouts, cycling followed immediately by a run, prepare your legs for the race transition.

Nutrition and Pacing

In longer races, pacing and nutrition matter as much as fitness. Half and full Ironman athletes eat and drink on the bike to fuel the run, and those who ride too hard often walk much of the marathon. Setting a target power or heart rate for the bike, and a conservative early run pace, usually produces the best finish. Use the calculator to test how a slightly slower bike and a stronger run change the total.

Comparing Races

Courses differ: hilly or windy bike legs, sea swims and hot runs all slow finish times. Comparing your predicted time with past results on the same course gives a sense of how realistic your paces are, and helps you choose where you would place in your age group.

Your First Triathlon

For a first sprint race, aim simply to finish comfortably. Practise open-water swimming if the race is not in a pool, check the bike route, and walk through the transition area beforehand so you know where your bike is racked.

Age-Group Racing

Most triathletes race in five-year age groups. Results from previous years show what times win or place in your group.

Equipment

Wetsuits, aerodynamic bike positions and race shoes can each save minutes, but training consistency matters far more.

Understanding Your Result

The headline gives the predicted finish time.

The splits line gives each leg and transition.

The share of race line shows how time is distributed.

The paces line gives bike pace per km and run speed.

When Should You Use This Calculator?

Use it to set a goal time before a race.

Use it to see how improving one discipline changes the finish.

Use it to plan pacing for each leg.

Common Mistakes

Using pool pace for open water. Allow for sighting and conditions.

Ignoring transitions. They can add several minutes.

Riding too hard. It slows the run.

Using fresh run pace. Running after cycling is slower.