First Triathlon Decision Engine
Which triathlon should your first one be — and what is actually standing in the way?
Answer six questions about where you are right now. You will get a recommended race distance, an honest readiness verdict, the specific gaps to close before race day, and a week-by-week roadmap that fits the hours you actually have.
On track — close the gaps first
Start with a Sprint — 750m swim · 20km ride · 5km run
You can swim but still rest between laps, and you have 12 weeks. That is enough runway to build a continuous 750m, so a Sprint is a realistic and appropriately stretching first target.
Where your readiness sits
View as a table
| Band | Score |
|---|---|
| Early days | 0–44 |
| On track | 45–69 |
| Ready | 70–100 |
| You | You — 47 |
Readiness is scored across six dimensions — swim, run, bike and equipment, weekly hours, training background and lead time.
Your readiness, dimension by dimension
Each dimension scored out of 100. The shortest bar is where your next block of work belongs.
View as a table
| Dimension | Score | Your answer |
|---|---|---|
| Swim | 25 / 100 | I can swim, but I stop and rest every lap or two |
| Run | 67 / 100 | About 5km |
| Bike & equipment | 67 / 100 | Mountain bike or hybrid |
| Time available | 33 / 100 | 3 to 5 hours |
| Training background | 33 / 100 | Recreationally active (gym, social sport) |
| Lead time | 67 / 100 | 12 weeks |
Preparation gaps to close
Ordered by what will actually stop you on race day.
- Swim continuity — you need 750m unbrokenResting on the wall is fine in a pool and impossible in a race. Build to 750m continuous before race day, adding roughly 10% to your longest unbroken swim each week.
- No open-water experiencePool metres do not transfer straight to open water. Sighting, no wall to rest on, other swimmers and cold-water shock are all separate skills. Get at least three supervised open-water sessions in before race day.
- Mountain bike or hybridNot a blocker. Over 20km it costs you a few minutes against a road bike and nothing else. Race on it. Consider swapping the knobbly tyres for slicks — the cheapest speed you will ever buy.
- No wetsuitHire one. The buoyancy makes a first open-water swim materially calmer, and most races are wetsuit-legal. Swim in it at least once before race day — a wetsuit changes your stroke and feels restrictive across the chest the first time.
Your 12-week roadmap
Segment width is how many weeks each phase gets.
View as a table
| When | Phase | Length | What you do |
|---|---|---|---|
| Weeks 1–4 | Base — build the habit | 4 weeks | 4 sessions a week, all easy enough to hold a conversation. Swim two of them. The goal of this phase is turning up, not getting fit — consistency here is what makes the rest work. |
| Weeks 5–8 | Build — add race-specific work | 4 weeks | Hold 4 sessions a week and extend the longest swim, ride and run. Add one brick session (ride straight into a short run) every week from here — this is the single highest-value session for a first-timer. |
| Weeks 9–10 | Race preparation — rehearse the day | 2 weeks | Swim open water in your wetsuit. Practise both transitions in the driveway until they are boring. Do one session at race effort over roughly half the race distance, in the kit you will actually wear. |
| Weeks 11–12 | Taper — arrive fresh | 2 weeks | Cut volume by about 40% and keep the frequency and a little intensity. Nothing you do in this phase makes you fitter; plenty of things you could do would make you slower. Sort logistics, not fitness. |
Phases scale to the time you actually have. Fewer weeks compresses base and build — it never removes the taper.
Why not a longer distance
An Olympic distance is roughly double this in every leg, and the difference in preparation is more than double — the swim in particular moves from something you can survive to something you must be able to pace. Race a Sprint first, then use what you learn about your transitions and fuelling to decide whether to step up this season or next.
Tri Alliance sessions that close these gaps
- Coached pool swim squad Coach-on-deck correction is worth more than any amount of solo lap swimming when you are building continuity.
- Supervised open-water session Supervised, with coaches on the water — the safe place to have your first open-water experience rather than on race morning.
- Brick session (bike into run) The bike-to-run transition is the part of a triathlon no single-sport training prepares you for.
The short answer
For most people, the right first triathlon is a Sprint distance (750m swim, 20km ride, 5km run) with a 12-week preparation block. The deciding factor is almost never running or cycling fitness — it is whether you can swim 400m continuously without stopping, and whether you have swum in open water. A Fun Tri or Super Sprint (300m swim, 8km ride, 2km run) is the correct starting point for anyone who cannot yet swim 400m continuously.
How to use this tool
- Tell the tool your endurance background and how many hours a week you can genuinely train.
- Rate your swim honestly — whether you can swim 400m continuously is the single biggest factor in the recommendation.
- Enter your longest current run, the bike you have access to, and whether you can get a wetsuit.
- Set how many weeks remain until your target race and what you want out of the day.
- Read the recommended distance, close the flagged preparation gaps, and follow the phase roadmap.
Common questions
What distance should my first triathlon be?
A Sprint (750m swim, 20km ride, 5km run) is the right first triathlon for most people who can already swim 400m continuously and have 8–12 weeks to prepare. If you still rest between laps, start with a Fun Tri or Super Sprint (300m swim, 8km ride, 2km run) — the swim is the leg that ends first triathlons, not the run.
How long do I need to train for my first triathlon?
Twelve weeks is the standard preparation block for a first Sprint triathlon on 3–5 hours a week. Six to eight weeks is achievable if you already run or ride regularly and can swim continuously. Under six weeks, drop the target distance rather than compressing the build.
Can I do a triathlon on a mountain bike or hybrid?
Yes. For a first Fun Tri or Sprint, a mountain bike or hybrid is completely acceptable and every club sees them on the start line. It costs you a few minutes over 20km, which matters only if you are chasing an age-group placing. Do not delay your first race to buy a road bike.
Do I need a wetsuit for my first triathlon?
For open-water races in Australian conditions a wetsuit is usually optional but strongly recommended for beginners — the buoyancy makes a first open-water swim substantially easier and calmer. Wetsuits can be hired for a single race. Never race in a wetsuit you have not already swum in at least once.
Should my first triathlon be a 70.3 or Ironman?
No. A 70.3 or full-distance race should never be a first triathlon. Do a Sprint or Olympic first so that transitions, open-water starts, pacing and race-day fuelling are already known quantities before you take on a race where a mistake costs you hours rather than minutes.