Calculating Percentile Rank Using Relative Strength Ranking

I have a spreadsheet of stock quotes that contains Relative Strength Ranking (RSR) ranging from -45 to 65 and the count of ranks is 1500. Could someone please explain how I can calculate percentile ranks using these numbers? Is there a specific formula?

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If the total number of stocks is exactly 1500, the percentile rankis $\frac {(\text {number below + number tied/2)}100}{1500}$. So if a stock has 579 stocks with lower RSR and 44 with the same RSR, its percentile rank is $\frac {(579 + 44/2)100}{1500}=\frac{60100}{1500}\approx 40.06$. Some people then round to the nearest whole number, or truncate, or something like that.