This is a rating performance calculator for ELO ratings (chess, for example). Rather than using the conventional "batch" formula however, this calculator calculates the "true" performance rating. That is, the rating for which predicted performance matches actual performance.
This is done using two methods: the Logistic method uses the logistic curve to predict performance, which corresponds with performance predictions used by USCF, ICCF and others. THe Normal method uses a normal CDF function to predict performance, which corresponds with the FIDE methods for performance prediction.
Neither of these methods calculates "FIDE Performance ratings" as used