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Swimming Pace and Interval Builder

· Last updated：2026-06-18

This tool is for informational purposes only and does not constitute medical, financial, or legal advice; consult a qualified professional for advice.

Convert swim benchmark times into 25m, 50m, and 100m pacing and generate CSS-style threshold intervals

Details

What this tool helps you do

Turns a swim benchmark into split targets and send-off based interval sets so athletes and coaches can build threshold-oriented pool sessions quickly.

Execution

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Written by the Elysia Tools team
HTML/CSS86
Health54
CSS48

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Health
Input types
number
Output type
json
Sample coverage
4
API ready
Yes

Overview

The Swimming Pace and Interval Builder converts benchmark swim times into precise pacing targets for 25m, 50m, and 100m distances, generating Critical Swim Speed (CSS) threshold interval sets with custom send-off times.

When to use

  • When planning structured pool workouts based on a recent time trial or benchmark swim.
  • When calculating exact target splits for 25m, 50m, or 100m intervals to maintain a consistent threshold pace.
  • When designing send-off times for swim squads or individual training sessions to ensure proper rest ratios.

How it works

  1. 1Enter your benchmark swim distance and the time it took to complete it.
  2. 2Specify your pool length along with your desired interval distance, repeat count, and rest period.
  3. 3The tool calculates your target split paces and generates a structured interval set with calculated send-off times.

Use cases

  • Coaches generating customized send-off times for swim squad lane groups based on varying fitness levels.
  • Triathletes calculating precise 100m pacing targets for CSS threshold sets in a 25-meter pool.
  • Fitness swimmers structuring a 10x100m interval workout with consistent rest periods.

Examples

1. Calculating CSS Intervals for a 400m Time Trial

Triathlon Coach

Background

A coach needs to set up a threshold set of 10x100m for an athlete who recently completed a 400m benchmark swim in 6 minutes (360 seconds).

Problem

Manually calculating the 100m threshold pace and adding a 15-second rest to find the exact send-off time.

How to use

Set the benchmark distance to 400m, benchmark time to 360 seconds, pool length to 25m, interval distance to 100m, repeats to 10, and rest to 15 seconds.

{
  "benchmarkDistanceMeters": 400,
  "benchmarkTimeSeconds": 360,
  "poolLengthMeters": 25,
  "repeats": 10,
  "intervalDistanceMeters": 100,
  "restSeconds": 15
}

Outcome

Generates a target pace of 22.5 seconds per 25m and a send-off time of 105 seconds (1:45) per 100m interval.

2. Pacing 50m Repeats in a Long Course Pool

Master Swimmer

Background

A swimmer wants to run a high-intensity threshold set of 20x50m in a 50m Olympic-sized pool based on their 100m benchmark of 80 seconds.

Problem

Determining the correct pace splits and send-off times for a 50m pool with 10 seconds of rest.

FAQ

What is a CSS-style threshold interval?

It is a training pace designed to match your Critical Swim Speed, helping improve aerobic capacity by using structured send-off times.

How does the tool calculate the send-off time?

It adds your target interval pace to your desired rest time, rounding to a practical send-off interval.

Can I use this for both 25m and 50m pools?

Yes, you can set the pool length option to either 25 or 50 meters to match your training facility.

What benchmark distance should I use?

Typically, a 100m or 400m time trial benchmark is used to establish baseline threshold paces.

What does the output JSON contain?

It provides calculated split paces (such as pace per 25m) and the final send-off time in seconds for your interval set.

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How to use

Input a 100m benchmark distance, 80 seconds benchmark time, 50m pool length, 20 repeats of 50m intervals, and 10 seconds of rest.

{
  "benchmarkDistanceMeters": 100,
  "benchmarkTimeSeconds": 80,
  "poolLengthMeters": 50,
  "repeats": 20,
  "intervalDistanceMeters": 50,
  "restSeconds": 10
}

Outcome

Calculates a 50m split pace of 40 seconds and sets a send-off interval of 50 seconds per repeat.