How to use the Swimming Pace Calculator

Time → Pace: enter a distance and your time to get pace per 100 m or 100 yd.
Pace → Time: enter a pace per 100 m and a target distance to predict your time.
CSS: Critical Swim Speed, calculated from a 400 m and a 200 m time trial.

Swimming pace reference

Level	Pace per 100 m
Beginner	2:30-3:00+
Intermediate	1:45-2:30
Competitive age-grouper	1:20-1:45
Elite	<1:10

What is Critical Swim Speed (CSS)?

CSS is the swimming equivalent of lactate threshold, the fastest pace you can sustain aerobically for a long swim. It is calculated from two maximal time trials:

CSS (m/min) = (400 − 200) / (T400 − T200)

Then convert to pace: pace (min/100 m) = 100 / CSS.

Training at CSS intensity for 20-40 minutes per session is highly effective for improving swimming fitness and open-water performance.

Pool lengths and yards vs meters

25 m pool (short course meters / SCM), most common worldwide
50 m pool (long course meters / LCM), Olympic standard
25 yd pool (short course yards / SCY), common in the USA

1 yard = 0.9144 meters. A 25-yd pool is slightly shorter than a 25-m pool, so pace per 100 yd is slightly faster than per 100 m at the same effort.

UK swimming context

Most UK public leisure centre pools are 25 m (short course). 50 m pools are less common , major ones include the London Aquatics Centre, Manchester Aquatics Centre, and Glasgow National Swimming Academy.

Swim England classifies competitive swimmers in performance categories. Open water swimming is particularly popular in the UK , events like the Great North Swim (Windermere), Swim Serpentine (Hyde Park), and Blenheim Triathlon attract large fields. Open water paces are typically 10-20 sec/100 m slower than pool pace due to wetsuits, navigation, and conditions.