Swim Time Prediction Tool

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This site provides some resources to help improve your swimming. In particular, it provides a calculator that will estimate your swim potential based on two swims over difference distances. For best results, it is advised that you use recent swims and use two distances that have a reasonable range (i.e. 100m and 1500m).


Fill in the relevant details and hit calculate.

Click to predict times over a range of distances! (Original Calc)

Click to predict your required 100m time for YYYYm in XX:XX!

First Swim

Distance: metres

Time: hours minutes seconds

Second Swim

Distance: metres

Time: hours minutes seconds

(Optional) Target Predictions

Calculate this: yes no


If enabled, predicted target times will be calculated using the TFD as defined above. 1.06 is considered a good rate of decay for triathletes. The expected improvement (EI) column denotes the potential gains that you could see should you train well!

Target Distance & Desired Time

Distance: metres

Desired Time: hours minutes seconds

Suspected SDI:


  • It is recommended that you calculate your existing SDI using the other calculator.
  • If you set SDI to 1.0, it will give you your required 100m split time.

For reference: SDI < 1.05 would suggest that you are one paced or very fit. SDI > 1.09 would suggest that you are good at sprinting or out of shape. If your SDI is low, but your times are poor, you would probably benefit from sprint training. Conversely, if your SDI is high and your sprint times are good, you should do some endurance work.