A few notes:
1. make sure to put zeros in boxes when minutes or seconds are zero. They are necessary.
2. distances less than 50 yards are probably somewhat meaningless, leading to misleading results.
3. this model is not a linear interpolation or extrapolation, as a few experiments will show.
4. you may use distances quite far apart, like 50 and 1650, and still get fairly accurate predictions.
5. one use of this model might be to predict 500-1650 performances for novices after a T-30 test.
6. as long as you do not change units in the middle of the calculation, you may use yards or meters (actually, this algorithm works quite nicely for running performaces at 400 meters and above).
7. you can also use the predictor to predict short course to long course and vice versa. For example, since 200 meters is 218.688 yards, you could put in times for the 100 and 200 (yards), and predict the time for 218.688. You should then add 4 seconds, since there are 4 more turns (which aid times about 1 sec per turn) in the 200 yards than there are in the 200 meters.
8. coaches can use the predictor to assess the value of practice times at odd distances.
9. if you have problems, try clicking on the reset button, and re-enter your data (putting in zeros, whenever appropriate).
10. have fun.
I also have developed an Excel spreadsheet that does much more than the predictor. It allows the user to experiment with the effects of pace (varying splits) on the total time for various races. How fast a first 50 can a particular swimmer swim, without severe effects later in the race? If a particular swimmer brings back a 500 very fast, what would they have been able to do if they had spread their energy more evenly over the whole race? The Excel-based model attempts to answer some of these what-if's. If you are interested in getting a copy of my Predictor/Pacing spreadsheet,e-mail me.