Need clarification on operator's performance rating calculation? Read this post.

What is a performance rating calculation? Suppose, Process Bottom Hem Observe time = 40 seconds and Standard Time = 30 seconds. So, what would be the exact calculation?

1. P.R = 40*100/30 = 133%
2. P.R = 30 *100/40 = 75%
Which one is correct? Will you please rectify my confusion?


Remember, normally operator's performance rating (PR) is not calculated from standard time and observed time. Instead, the operator's performance rating is assessed by a work-study officer who conducts time study for an operation.

To answer this question, I will consider that we are going to do the reverse method.

There are the steps for calculating standard time from time study and observed time. The steps are explained in an earlier post How to calculate standard time from Time Study.

First, know the steps of calculating standard time

You record the observed time. Then you calculate normal time from the observed time. Normal time = (Observed time x Performance rating). Then from the normal time, we calculate standard time by adding allowances (machine allowance + contingency allowance + personal fatigue allowance + bundle handling allowances).

(Normal time + Allowances percent) = Standard time

You need to deduct allowances from the standard time.

Therefore, the PR calculation formula would be

= ((Standard time – Allowances) / Observer time) x 100

In your example, the standard time is 30 seconds and the observed time is 40 seconds and you don’t have an allowance percentage. Let’s assume the allowance is 0 seconds (for calculation purposes). From that, we can derive PR values as the following.

So, performance rating (PR)= ((Standard time – Allowances) / Observed time) x100= ((30-0)/ 40 seconds) x 100 = 75%

In your example, the second equation is correct.

Note: The reverse calculation may not be accurate. But for learning and comparing your rating, you can use this method.

To learn more about operator performance rating read the following titles
  1. The concept of performance rating
  2. An Interesting Question on Garment SAM Calculation and Use of Rating Factor
  3. How to Use Performance Rating Calculating Basic Time?
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