Zerdly

Swim Time Predictor

Predicts swim finish time from distance and pace per 100 metres.

100% FreeRuns in your browserBasic
How to use this calculator

Enter details

Distance(m)
Pace per 100 m
:

Result

Fill in the fields to see your result.

Estimate only — real results depend on terrain, weather, fatigue, conditions and individual fitness. Not medical or coaching advice.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter the distance (m) and your pace per 100 m.
  2. Read the estimated swim time and speed.

How it works

Time = (distance ÷ 100) × pace per 100 m.

Worked example

1500 m @ 1:50/100 m. = 27:30.

Common mistakes

  • Predicting across very different distances — accuracy falls as the gap from your known swim grows.
  • Ignoring that open water is slower than the pool — predictions assume similar conditions.

Tips

  • Times are estimates only — not medical or coaching advice. Always train safely and follow event rules.
  • Distances are editable: choose “Custom…” to enter your own course lengths.

Frequently asked questions

How does the swim time predictor work?

It scales your known time by the distance ratio raised to a fatigue exponent (a Riegel-style model), so longer swims are predicted slightly slower per 100 m.

How accurate is it?

Best within roughly double or half your known distance and in similar water; large jumps such as 50 m to 5 km carry more error.

Pool or open water?

This assumes a steady pool pace. Open water is usually slower — use the Open Water Swim Time calculator.

Related tools

Explore more in Health, Fitness, Nutrition & Body.

Cite this tool

Zerdly. (2026). Swim Time Predictor. Retrieved from https://www.zerdly.com/tools/swim-time-predictor/

Tip: Enter any known values to calculate the remaining results.

All calculations run in your browser. Your inputs are never saved or transmitted.