Swimming Pace Calculator

About the Swimming Pace Calculator

Swimmers measure speed differently from runners and cyclists. Instead of kilometres per hour or minutes per kilometre, swimming pace is given as the time to swim 100 metres — or 100 yards in many American pools. Pace per 100 is written on pool clocks, in training sets and in triathlon plans, so it is the number worth knowing.

This swimming pace calculator works in three ways. It finds your pace per 100 from a time and distance, the finish time for a distance at a given pace, and your critical swim speed (CSS) from two time trials. It converts between metres and yards, gives your speed in km/h, and shows finish times for common pool and triathlon distances, from 100 metres to the 3.8 km Ironman swim.

How to Use the Swimming Pace Calculator

Choose Pace from time, Time from pace or Critical swim speed.

For pace, enter the time as m:ss or h:mm:ss and the distance.

For a finish time, enter the pace per 100 and the distance.

For CSS, enter your all-out 400 and 200 times.

Choose metres or yards for the pool.

The Formulas

  pace per 100      = time ÷ distance × 100
  finish time       = pace per 100 × distance ÷ 100
  pace per 100 yd   = pace per 100 m × 0.9144

  critical swim speed:
      CSS (m/s)         = (400 − 200) ÷ (T400 − T200)
      CSS pace per 100  = (T400 − T200) ÷ 2

Step-by-Step Examples

1,500 metres in 30:00.

  30:00 = 1,800 seconds
  1,800 ÷ 1,500 × 100 = 120 seconds → 2:00 per 100 m
  per 100 yd: 120 × 0.9144 = 109.7 s → 1:50
  speed: 3.00 km/h

An Ironman swim at 2:00 per 100 m.

  2:00 × 3,800 ÷ 100 = 76 minutes → 1:16:00

Critical swim speed from a 400 in 6:40 and a 200 in 3:10.

  6:40 − 3:10 = 210 seconds for the extra 200 m
  210 ÷ 2 = 105 seconds → CSS 1:45 per 100 m

Triathlon Swim Times by Pace

  Pace/100 m   750 m    1,500 m   1.9 km   3.8 km
  1:30         11:15    22:30     28:30    57:00
  1:45         13:08    26:15     33:15    1:06:30
  2:00         15:00    30:00     38:00    1:16:00
  2:15         16:53    33:45     42:45    1:25:30
  2:30         18:45    37:30     47:30    1:35:00

What Is Critical Swim Speed?

Critical swim speed is a swimmer's version of threshold pace: the fastest pace you could in theory sustain for a long time without tiring. It is estimated from two maximal efforts, usually a 400 and a 200, swum on the same day with full recovery between them. Because both swims include a similar sprint start and a similar all-out finish, the difference between them — the extra 200 metres — reflects your sustainable aerobic speed. In practice, CSS is roughly the pace a trained swimmer can hold for about 30 minutes.

Training with CSS

Many coaches and triathlon programmes set training paces from CSS. Threshold sets, such as 10 × 100 metres with short rests, are swum at about CSS pace. Longer endurance sets are swum a few seconds per 100 slower, and speed work faster. As fitness improves, CSS gets faster, so it is worth retesting every 6 to 8 weeks. Keep the test conditions the same — same pool, similar time of day and the same warm-up — so the results are comparable.

Metres and Yards

A yard is 0.9144 metres, so 100 yards is 91.44 metres and swimming 100 yards takes about 8.6 percent less time than 100 metres at the same speed. A pace of 1:40 per 100 yards is about 1:49 per 100 metres. Pools in the United States are often 25 yards long, while most of the rest of the world uses 25 or 50 metre pools. Always check the pool length before comparing times.

Pool and Open Water

Pool times are faster than open-water times at the same effort. In a pool, every length ends with a push-off from the wall, a free burst of speed that open water does not give. Outside, swimmers also need to lift their heads to sight, deal with waves, currents and cold, and swim around other people. A wetsuit adds buoyancy and can offset some of the difference. Most triathletes find their open-water pace several seconds per 100 slower than their pool pace, so allow for it when predicting race times.

Improving Your Swimming Pace

For most adult swimmers, technique limits speed far more than fitness does. Water is around 800 times denser than air, so a streamlined body position and an efficient catch save more time than extra effort. Drills that focus on body rotation, a high elbow and a long, relaxed stroke usually bring faster gains than simply swimming more laps. Interval sets at or just below CSS then build the fitness to hold the faster pace for longer. Recording your pace per 100 regularly shows whether the changes are working.

Pacing matters as much as speed. Many swimmers start a long set or race far too fast and fade badly; holding an even pace per 100 from the first length to the last is almost always quicker overall. Use the pool clock to check each 100 against your target.

Understanding Your Result

The headline is your pace per 100, the finish time, or your CSS, depending on the mode.

The pace line gives the pace per 100 metres and per 100 yards.

The speed line gives the speed in km/h and metres per second.

The times at this pace line gives finish times for 100 m, 400 m and the sprint, Olympic, 70.3 and Ironman triathlon swims.

When Should You Use This Calculator?

Use it to work out your pace from a timed swim or race.

Use it to predict your time for a triathlon swim.

Use it to find your CSS and set training paces.

Use it to convert between yard and metre pools.

Common Mistakes

Mixing yards and metres. Check the pool length before comparing paces.

Testing CSS without full effort. Both trials must be all-out for a fair result.

Resting too little between trials. Take full recovery before the second swim.

Expecting pool pace in open water. Allow several seconds per 100 for conditions.