Estimated VO2max is another method, which estimates your maximum possible usage of oxygen. This also generally corresponds to performance. Calculations for estimated vo2max (from Matt Mahoney's program) v = 1609.3/pace; /* calc meters/mile*/ /* VO2 and percent_max based on "Jack Daniels, Conditioning for Distance Running - The Scientific Aspects", Wiley & Sons, 1978 */ vo2 = -4.60 + 0.182258*v + 0.000104*v*v; percent_max = 0.8 + 0.1894393*exp(-0.012778*minutes) + 0.2989558*exp(-0.1932605*minutes); vo2max = vo2/percent_max; minutes is total minutes run. exp(-0.012778*minutes) means e raised to the power of (-.012778 times minutes) percent of VO2max = percent_max*100