A Four-Part Series:
      Age Grading
      Age Grading - Calculation Notes
      Age Grading - Non-Standard Distances
      Age Grading - Calculator
 
I frequently get questions about using the calculator to compute age-graded performance percentages for non-standard distances (e.g., 8 miles). The tables do not report values for those distances so the calculator can not make calculations for them either. BUT, there is a way to age grade performances at non-standard distances that might be accurate enough (and fair enough) to allow you to include one or more such races in a series of age-graded races. Let me explain.
 
When you graph the anticipated paces for any age/gender cohort over all the standard distances, you get a fairly smooth curve that allows you to then estimate the performances at intermediate, non-standard distances. Those estimates can be expressed as an adjustment factor that can be applied to output from the calculator using the next shorter standard distance. Let's look at one example.
 
Six walkers complete a 15K race. Their times are shown in Column B of the table at right. Using the age grading calculator, we can compute their age-graded performance percentages at 15K (see Column C). That was easy ... but ... if 15K was not a standard distance, we could also compute their age-graded performance percentages using the 10K distance (see Column D) and then make an adjustment. But what adjustment would we use? In this case, we can compute their age-graded performance percentages at both 15K and 10K, and use the average ratios between them (see Column E). Notice that all of the ratios in Column E are about the same (and their average is 1.5249).
 
If 15K was a non-standard distance, we could multiply the 10K percentages by the average ratio (see Column E) and estimate the 15K percentages (see Column F). There is a slight difference in the computed (Column F) and actual (Column C) percentages, so you would not want to estimate the percentages for a standard distance ... but ... as a technique for estimating the percentages for non-standard distances, it may be close enough for what you want to do. You have to decide. Some might be helped by rounding and others hurt by it--but that is also true given the nature of the age-grading tables (with times rounded to whole seconds) and the calculator (which rounds the percentages to 2 decimal places).
 
By my best calculations, you should use the values at left in age grading non-standard distances. For example, to age grade an 8-mile race, enter the actual finish time in the calculator using the 10K distance; then multiply the age-graded performance percentage for 10K by 1.3052 to obtain the estimated percentage for the 8 miles.
 
IMPORTANT NOTES:

• The age-graded performance percentages generated by the method noted above WOULD NOT BE OFFICIAL in the formal world of masters track and field. They would only be valid to the degree you and your peers agree that they are.
   
• These values are based on the race walking tables and may not be as accurate for the running tables.