The Formula Behind Feedback Percentages

[Do you have a negative or two? Ever wonder when you might receive enough positives to push your Feedback score back up to 100% positive? Well, I thought I might share with you a recent email regarding exactly how eBay calculates the "positive percentage" displayed next to a member's Feedback score. Warning! 5th grade math ahead! -Griff]

Hi Griff,

I recently noticed a seller who has received 3 negatives this month yet his feedback still shows 100% positive. How can this be?

A concerned seller

My response:

Hello Concerned,

Nothing amiss here. Let me explain, step-by-step, how the percentages for eBay Feedback are calculated.

First, here is the section of the seller's feedback page for reference:

Feedback Score: 3254 
Positive Feedback: 100%
 
Members who left a positive: 3255
Members who left a negative: 1
 
All positive Feedback: 4161

The seller has indeed received three negatives but they are all from the same User ID. When calculating percentages, multiple feedbacks from the same User ID count only as one negative. That is why the page states "Members who left a negative: 1"

With this fact in mind, eBay uses a straightforward formula to calculate the number displayed as "Percentage of Positives":

Unique Positives ÷ (Unique Positives + Unique Negatives)= percentage

In this case, the seller has received unique 3255 positives and 1 unique negative. That results in

3255 ÷ 3256 = 0.99969287469287469287469287469287

In this equation, 100% is indicated by a score of 1. The rule is, we round up the number based on the amount of number in the fourth decimal place to the right of the decimal. In this case, the fourth place shows a six so round the number to 1.00000 etc.

By the way, if the seller had two unique negatives, the equation would have read 3255 divided by 3257 which equals 0.99938593797973595333128645993245. Since the fourth decimal place to the right of the decimal point is a 3, we would not round it up thus the seller's feedback percentage would
drop to 99.93%. Since we only show to the tenths of percentage, the number would display as 99.9%.

One of our intrepid members has actually created an online Feedback calculator that implements this formula in an easy-to-use format. Using it shows us some interesting facts. For example, if a seller has one unique negative, their percentage score will go back to 100% once their unique positives reach 1999. As for our seller, if he receives a second unique negative, he will have to earn a total of 3998 unique positives (and no other negatives) in order to reach 100% again.

Regards,

Griff