NPS Calculation is a simple equation that is calculated by subtracting the percentage of detractors from the percentage of promoters who have responded to a standard NPS (Net Promoter Score) question... but hang on, that sounds quite complicated.
Let me explain these various elements, and I'll start with what is a standard NPS question: it's deceptively simple and is worded as:
Those viewing the survey question see a scale of 0-10 (where 0=not at all likely to recommend the product, and 10=extremely likely to recommend the product).
In the NPS methodology, responses are organized into three groups that are based on the scoring:
Scores of 0-6 are called detractors
Scores of 7-8 are called passives
Scores of 9-10 are called promoters
So, finally to your question: the NPS score is calculated by subtracting the percentage of detractors from the percentage of promoters; we ignore the passives for the calculation.
The NPS score is displayed as a number (not as a percentage) and can be within the range of -100 to +100.
Here's a worked example:
Let's take a look at how to calculate the NPS for responses to your survey over the course of a day. In this example, you've had 10 respondents and they have given your product the following scores:
3, 4, 5, 6, 8, 8, 8, 9, 10, 10
If we arrange these into detractors, passives and promoters, this equates to:
four detractors (3, 4, 5, 6), ie 40% of the responses
three passives (8, 8, 8), ie 30% of the responses
three promoters (9, 10, 10), ie 30% of the responses
So the day's NPS = -10 (calculated by: 30% promoters - 40% detractors = -10)