The same formula can provide the percentage of detractors (e.g., 100/500 x 100 = 20%). Your NPS is the percentage of promoters minus the percentage of detractors.

More than two-thirds of the Fortune 1000 companies use the Net Promoter Score (NPS), making it one of the most widely recognized and commonly used metrics among practitioners (Baehre et al., 2022, ...

To determine your official NPS score, take the percentage of promoters (nines and 10s) and subtract the percentage of detractors (sixes and lower). That number is your Net Promoter Score.