Free swim tool
Open-Water Swim Split Predictor
Your pool pace + the conditions in. A realistic race swim split out.
Open water is a projection, not a promise. Conditions move it.
Why pool pace doesn't transfer to open water
Your pool pace is a clean number: flat water, a black line, and a wall to push off every length. Race day removes all of that. The same engine that holds 1:45 in the pool will read slower in open water, and the gap is rarely small.
Five things move your real race split: sighting (lifting your head to navigate costs rhythm), no walls (no push-offs to recover speed), the wetsuit (buoyancy that usually makes you faster), chop (wind and waves disrupt the stroke), and the mass start (contact, drafting, and pacing chaos in the first minutes).
Open-water /100 ≈ pool /100 × condition factorsWhat this tool does
It takes your pool pace and applies realistic condition factors for wetsuit, sighting, and water state, then projects a race swim split as a range, not a single fake-precise number. Use it to set expectations, not to print a finish time.
One thing to expect: in calm water, with a wetsuit and confident sighting, the wetsuit's buoyancy can offset, or even cancel, the open-water penalty, so your projected split can land close to, or a touch faster than, your flat pool pace. Add chop or shaky sighting and the penalty comes back.
Open-water swim FAQ
Why is open water slower than the pool?
No walls to push off, sighting that breaks your rhythm, chop that disrupts the stroke, and a mass start that scrambles pacing. Most swimmers lose several seconds per 100 versus their clean pool pace.
Does a wetsuit make me faster?
Usually yes. The added buoyancy lifts your hips and reduces drag, which is typically worth a few percent. This tool models a wetsuit as a small speed gain when you select it.
How accurate is this prediction?
Treat it as a projection range, not an exact race prediction. It is a planning estimate based on typical condition factors; your real split depends on the day, the course, and your sighting on the swim.
How do I get better at open water?
Practise sighting and open-water reps, and build propulsion that holds when you fatigue. A stroke that produces steady Propulsive Watts in the back half of a race is what closes the gap conditions create.
The predictor shows the gap. Propulsion closes it.
This tool shows you the gap conditions open up between your pool pace and your real race split. What closes that gap isn't a calculator, it's propulsion that holds under fatigue plus open-water reps. ZWIM measures the first part as Propulsive Watts, so the stroke you bring to the start line still produces force when the back half hurts.
And the gap is widest for swimmers who can't get to the pool often enough to build that engine. Connected Swim Training is built for exactly that: the days between pool sessions, when most plans quietly fall apart.
Related swim tools
Project the split. Train the engine that holds it.
ZWIM is Connected Swim Training for home: real Propulsive Watts and a real game, for the days you can't get to the pool.
This is a projection range for planning, not an exact race prediction. Open-water results vary with conditions, course, and the day. ZWIM helps you train between pool days; it does not replace pool swimming and does not eliminate open-water uncertainty.