Percentile and percentage are not directly interchangeable
Percentile shows relative position in a group
Percentage shows a part out of 100
To convert a percentile rank to a percentage, use the same numeric value only if you mean the rank itself
Example: 85th percentile means the value is higher than 85% of the group
Example: 85% means 85 out of 100
If you need the percentage of people below a percentile, use the percentile value
If you need the percentage above a percentile, subtract the percentile from 100
Example: 85th percentile = 15% above it
Use the context to decide whether you need percentile rank or percentage value