Triathlon finish-time scenario planner

What this finish-time predictor actually predicts

This page builds a longer-distance finish-time scenario from swim, bike, and run split times you enter. “Predictor” is the tool’s familiar name, but the result is an arithmetic scenario rather than a statistically validated forecast. It does not infer fitness, readiness, probability of finishing, or ability to meet an event cutoff. You choose the source splits, distance step, slowdown percentages, and target transition time; the page makes the consequences of those assumptions visible.

Enter each recent split in minutes and leave transitions out of those three fields. Choose one of the available steps: sprint to Olympic, Olympic to 70.3, or 70.3 to full distance. Then set a separate percentage adjustment for each discipline and enter the combined target T1 and T2 time in minutes. Use a source race that resembles the target in course, conditions, rules, and effort where possible. A personal best on a short, flat course may be a poor basis for a hilly long-course scenario.

The distance scaling and adjustment formula

For each discipline, the calculator multiplies the source split by a distance ratio and by one plus the adjustment percentage. In plain language:

Target split = source split × target-to-source distance ratio × (1 + entered adjustment ÷ 100)

The sprint-to-Olympic and 70.3-to-full steps use a ratio of 2 for all three sports. The Olympic-to-70.3 step uses 1.9 ÷ 1.5 for the swim, 90 ÷ 40 for the bike, and 21.1 ÷ 10 for the run. Those are the calculator’s chosen reference distances, not a statement that every event uses exactly those course lengths. Race formats and measured routes can vary, so compare these reference assumptions with the current organiser guide.

For example, with default sample split values of 15 minutes swimming, 40 minutes cycling, and 25 minutes running, a sprint-to-Olympic scenario with adjustments of 5%, 10%, and 15% produces 31.5 minutes for the swim, 88 minutes for the bike, and 57.5 minutes for the run. Add the entered eight minutes for transitions and the central scenario totals 185 minutes, or 3 hours 5 minutes. These numbers illustrate the current inputs only; they are not expected performances or recommendations.

The default sensitivity display adds and subtracts 5% of the combined moving time. Transitions remain unchanged. In the example, moving time is 177 minutes, so the displayed range is approximately 176 to 194 minutes after adding the eight transition minutes and rounding to whole minutes. That range is not a confidence interval or probability band. It is a fixed arithmetic sensitivity around the central scenario.

Choosing source splits that have meaning

Use official results or reliable training records for a comparable effort. Confirm what the timing split includes: some events place timing mats around transition differently, and official elapsed time can contain segments that a moving-time input excludes. If your source result contains transition time, remove it before entering the discipline fields, then enter a separate target transition estimate. Otherwise transition time is counted twice.

A pool swim and an open-water race do not automatically have the same pace. Navigation, start density, current, waves, visibility, turns, drafting rules, and the path to the timing mat affect the result. Cycling time depends on climbs, descents, surface, wind, turns, traffic management, equipment, and effort distribution. Running late in a long event can differ substantially from a fresh road race. The calculator has no fields for those details and will not adjust for them automatically.

Choose a percentage for each discipline based on evidence, not a desire for a particular total. Training on the longer distance, brick sessions, course profile, pacing discipline, likely conditions, and fueling rehearsal can all influence the assumptions you decide to test. If you do not have a strong basis for one percentage, create several cases rather than presenting a single precise number. A spreadsheet of assumptions is only useful when the inputs are honest about their uncertainty.

Build scenarios instead of chasing one answer

A practical approach is to create a central case and at least one slower case. Change the discipline percentages independently: for instance, use a cautious bike adjustment if the target course climbs more, and a separate run adjustment based on how you have performed after comparable rides. Keep transition time realistic for the target event layout. Avoid applying the same adjustment everywhere just because it is easy to type; the tool lets each discipline vary because their course and fatigue factors differ.

Change one assumption at a time to learn how sensitive the total is. If increasing the run adjustment by five percentage points moves the result by a large amount, the scenario depends heavily on that assumption. You may then want more relevant training evidence or a wider planning range. A faster result created by a negative adjustment is mathematically allowed within the field range, but it should have a clear basis, such as genuinely faster course conditions or a recent performance that better represents your current ability.

Do not use the output to decide that a race is safe, appropriate, or guaranteed. Compare target splits with current event cutoff and checkpoint times, taking account of when those clocks start and any race-specific rules. A finish time under the overall cutoff does not necessarily imply that each intermediate checkpoint is feasible. For a race schedule, use the organiser’s timing table, and ask a coach or qualified clinician for individual guidance when relevant.

Common sources of false precision

The model assumes that a source split scales by the selected ratio and your chosen adjustment. It does not use training volume, age, experience, power data, heart rate, elevation, heat, equipment, nutrition, transition layout, race-day incidents, or statistical results from similar athletes. It cannot distinguish an estimate from a verified split. The output shows hours and minutes, but its precision is limited by the assumptions you typed.

Course distances also require care. The Olympic-to-70.3 reference ratio uses 1.5 km to 1.9 km for swimming, 40 km to 90 km for cycling, and 10 km to 21.1 km for running. A particular event may differ, and a modified course can change late. Use the page to understand a rough scaling scenario, then replace the mental model with the current course map and guide when planning a specific event.

Related planning tools

Use the pace calculator to add discipline paces and transition estimates for a course profile. The transition-time estimator offers a separate way to examine time spent in T1 and T2. The race-day simulator can place your estimated schedule against race-day logistics, and the triathlon path builder can help compare which distance to explore next. Check each tool’s assumptions; none substitutes for the official cutoff schedule or a coach’s individual assessment.

Frequently asked questions

Is the displayed range a confidence interval?

No. It is a fixed ±5% adjustment to estimated moving time in the current implementation, with transitions left unchanged. It does not describe probability or model uncertainty statistically.

Should I enter a total time or moving splits?

Enter swim, bike, and run moving splits separately, in minutes. Leave transitions out and enter a target combined T1 plus T2 estimate in the transition field.

Does this tell me if I can finish an Ironman?

No. It scales split assumptions but does not assess training, health, cutoff checkpoints, course conditions, or readiness. Consult current event rules and qualified support when making a race decision.

Why does Olympic-to-70.3 bike time grow more than the other split ratios?

The current calculator uses reference distances of 40 km for the source ride and 90 km for the target ride. Actual courses and formats can vary, so use the event’s current published distance for real planning.