The 70.3 distance
Half Ironman is 1900 m swimming, 90 km cycling and 21.09 km running, totalling 113 km — hence 70.3 miles. It is long enough that fuelling becomes a fourth discipline: most athletes need 60–90 g of carbohydrate per hour on the bike to run well afterwards.
Where the sub-6 hour mark falls
A sub-6 hour 70.3 usually looks like a 40-minute swim, a 3:00 bike at 30 km/h, and a 2:05 run at 5:55 per kilometre, plus five minutes of transitions. The calculator lets you test which combination is realistic for your own paces rather than copying someone else's split.
Pacing the bike
Ride the 90 km at an effort you could sustain for about three hours, not at 40 km time-trial pace. The run follows, and it is unforgiving: a bike leg ridden 10% too hard typically costs 5–8 minutes on the half marathon. The run split tool shows the off-bike penalty explicitly.
Frequently Asked Questions
What is a good 70.3 time?
Under 6 hours is a common goal; 5:00–5:30 is competitive age-group; under 4:30 is elite.
How much carbohydrate do I need?
60–90 g per hour on the bike for most athletes, practised in training. More than that needs gut training.
Should the run pace be my open half marathon pace?
No — expect 5–8% slower, and more in heat. Enter the pace you have actually run off the bike.
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Privacy & your data
SwimRunPace calculates everything in your browser. Distances, times and body weights are never uploaded — there is no account, no server-side record and no training history stored between visits.