Triathlon Training Calculator
Enter your swim pace, bike speed, and run pace for any triathlon distance and this calculator works out your projected finish time including transitions. It also estimates how many months of training you need and how many hours per week to commit, based on your athletic background and your goal. Add your lactate threshold heart rate to get personalised five-zone training bands for all three disciplines.
How to use this calculator
Start by selecting your target race distance and units. Enter your expected swim pace in seconds per 100 metres (or yards), your average bike speed, and your run pace. T1 and T2 fields capture transition times - three to four minutes each is typical for age-groupers. The projected finish time updates instantly. Scroll to the training plan section and set your athletic background and race goal. The calculator returns the number of months to prepare and your weekly training hours target. Finally, enter your lactate threshold heart rate (LTHR) to unlock five personalised training zones across all disciplines.
Understanding the triathlon training zones
The five-zone model used here follows Joe Friel's system, which is the basis of USA Triathlon and British Triathlon coaching. Each zone is a percentage range of your lactate threshold heart rate (LTHR). Zone 1 (below 85 % LTHR) is pure recovery. Zone 2 (85-89 %) is aerobic base - the zone where the majority of your training volume should sit, because it builds mitochondrial density and fat oxidation without generating excessive fatigue. Zone 3 (90-94 %) is tempo, used sparingly. Zone 4 (95-99 %) sits at threshold and is the engine room for race-specific fitness. Zone 5 (100-106 %) is VO2 max work, used in short intervals to raise your aerobic ceiling. Most coaches recommend that 80 % of your weekly volume falls in Zones 1-2 and only 20 % in Zones 3-5, a principle known as polarised or 80/20 training.
How finish time is calculated
The calculator adds five components: swim time, transition 1, bike time, transition 2, and run time. Swim time = (swim distance / 100) x pace in sec/100 m. Bike time = distance / speed x 3600. Run time = distance x pace in sec/km. Transitions are simply your T1 and T2 inputs. There is no elevation, wind, or wetsuit adjustment in this tool, so treat the result as a flat-course baseline and add 3-8 % for hilly or hot conditions.
Training time estimates and weekly hours
Monthly training duration estimates come from USA Triathlon coaching guidelines and the published work of Dr. Joe Friel and Mark Allen. Athletes with no endurance background need more base-building time before adding intensity. The weekly hours range represents your average during the peak build phase, typically the 8-12 weeks before a taper. You do not need to hit the upper figure every week - build gradually at around 10 % per week, then cut back by 20-30 % every third or fourth week to allow super-compensation. The chart on this page shows a sample ramp through your build, with a three-week taper at the end.
Standard triathlon distances
| Format | Swim | Bike | Run | Typical finish (recreational) |
|---|---|---|---|---|
| Sprint | 750 m | 20 km | 5 km | 1:00 - 1:30 |
| Olympic | 1.5 km | 40 km | 10 km | 2:00 - 2:45 |
| Half (70.3) | 1.9 km | 90 km | 21.1 km | 4:30 - 6:30 |
| Full (140.6) | 3.8 km | 180 km | 42.2 km | 10:00 - 14:00 |
Official distances used by World Triathlon (ITU) and IRONMAN. Transition times are not included.
Frequently asked questions
What swim pace should a beginner triathlete use?
Most beginner triathletes swim 120-150 seconds per 100 metres (2:00-2:30 per 100 m). If you are not sure, swim 400 metres at a steady effort and divide the total time by four. Use that number as your race-day pace and then subtract 5-10 seconds as you improve with training. A pace of 110-120 sec/100 m is typical for an intermediate club-level swimmer.
What is a realistic bike speed for a triathlon?
Club-level triathletes typically average 28-34 km/h (17-21 mph) on a flat Olympic course. Beginners on a road bike without tri bars often average 22-28 km/h (14-17 mph). Elite age-groupers can sustain 36-40 km/h (22-25 mph) on a TT bike. On hilly courses, expect to lose 2-4 km/h versus a flat baseline.
How do I find my lactate threshold heart rate (LTHR)?
The simplest field test is a 30-minute all-out effort (run or cycle) done solo. Record your average heart rate for the last 20 minutes - that is a good approximation of LTHR. For cycling, a 20-minute FTP test gives a similar number. LTHR is not the same as maximum heart rate. Most adults have an LTHR of 150-175 bpm, but it varies significantly by age, fitness and genetics.
How long do I need to train for an Ironman?
Athletes with no endurance background need roughly 14-18 months of consistent training to finish an Ironman safely and comfortably. Recreational runners or cyclists with a modest base need about 10-14 months. Experienced endurance athletes can be race-ready in 7-10 months. These figures assume no significant interruptions. Rushing the build increases injury risk and diminishes race-day performance.
What is the 80/20 rule in triathlon training?
The 80/20 principle means roughly 80 % of your weekly training time is spent at low intensity (Zones 1-2, conversational effort) and only 20 % at moderate to high intensity (Zones 3-5). Research by Dr. Stephen Seiler and the coaching practice of elites such as Mark Allen support this distribution. Doing too much work in Zone 3 - the "moderate effort" zone - is a common amateur mistake that increases fatigue without delivering the training adaptation of either truly easy or truly hard work.
How do transition times affect my finish time?
Transitions are often called the fourth discipline of triathlon because they are "free" time - no extra fitness required, just organisation and practice. A two-minute improvement in transitions costs nothing physiologically. Recreational athletes average 3-5 minutes per transition at Olympic distance. At Ironman distance, T1 averages 8-12 minutes for age-groupers. Practicing your transitions in training can easily save 5-10 minutes off a long-course finish time.