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Bike Split Calculator

Turn an average speed into your bike split for any triathlon distance — or work out the speed you need for a target time. Works in mph or km/h. Free, instant, fully editable.

Your ride
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Your bike split
Bike time
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The bike is where most triathlons are won or lost. Riding even 1 mph easier "buys" you a fresher run — over-biking is the classic way to blow up. Plan a speed (and power) you can hold all day, not a 40 km TT pace.

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How bike splits work

It's simple math — distance ÷ average speed — but average speed is the slippery part: wind, hills, drafting rules and fatigue all pull it down from your fresh, flat numbers. The triathlon bike distances:

RaceBike distance
Ironman (140.6)112 mi / 180 km
70.3 (Half)56 mi / 90 km
Olympic40 km / 24.8 mi
Sprint20 km / 12.4 mi

A rough sense of speed: a sub-12 Ironman usually needs around 17–19 mph on the bike; a 5:30 70.3 wants ~18–20 mph. Hills and wind change that a lot.

Planning estimate only. Race a sustainable effort and protect your run.

Frequently asked questions

What speed do I need for a sub-12 Ironman?

Roughly 17–19 mph average over 112 miles, depending on your swim, run and transitions. Use the pace planner to balance all three legs against a goal time.

Why is my race speed slower than training?

Race courses have wind, climbs and no drafting, and you're holding back to save your run. Plan your bike split off a sustainable, all-day speed — not a short time-trial pace.