Process for estimating catalyst performance, hereafter: the estimation process, of catalyst used in refinery reforming processes for converting naphtha to gasoline, hereafter: the naphta reforming process, in which naphtha reforming process coke deposits are formed on the catalyst particles, which estimation process comprises: a. Conducting at least two catalytic reactions in parallel with the same catalysts in the same amounts in at least two parallel reactors, the catalysts being present as particulate matter in a fixed bed in these at least two reactors, these at least two reactors being operated at equal conditions for LHSV, pressure, and feed composition, the feed comprises naphtha and hydrogen, and the reactions in these at least two reactors being carried out for a different reaction time, b. Conducting the reactions under a. at a temperature that achieves a target RON, and adjusting the temperature during the reaction time to maintain said target RON during the reaction time under a., the temperature for the reactions with the same catalysts being adjusted to the same extent, and recording the reaction temperature required over at least 10 measuring points over the longest reaction time to give a temperature -time relationship, c. Measuring catalyst performance as expressed by yield of a target product for each of the catalytic reactions under a. over at least 10 measuring points over the reaction time for each of the reactions to give a yield - time relationship, d. terminating the catalytic reactions under a., wherein the at least two reactions are terminated after a different reaction time, and measuring the coke deposition on the catalyst particles and establishing the relationship of coke deposition as a function of reaction time for the catalyst used to give a coke deposition - time relationship, e. Using the temperature - time relationship of b., the yield - time relationship of c., and the coke deposition - time relationship of d. to calculate a yield - temperature relationship at a given coke deposition percentage. a. Conducting at least two catalytic reactions in parallel with the same catalysts in the same amounts in at least two parallel reactors, the catalysts being present as particulate matter in a fixed bed in these at least two reactors, these at least two reactors being operated at equal conditions for LHSV, pressure, and feed composition, the feed comprises naphtha and hydrogen, and the reactions in these at least two reactors being carried out for a different reaction time, b. Conducting the reactions under a. at a temperature that achieves a target RON, and adjusting the temperature during the reaction time to maintain said target RON during the reaction time under a., the temperature for the reactions with the same catalysts being adjusted to the same extent, and recording the reaction temperature required over at least 10 measuring points over the longest reaction time to give a temperature -time relationship, c. Measuring catalyst performance as expressed by yield of a target product for each of the catalytic reactions under a. over at least 10 measuring points over the reaction time for each of the reactions to give a yield - time relationship, d. terminating the catalytic reactions under a., wherein the at least two reactions are terminated after a different reaction time, and measuring the coke deposition on the catalyst particles and establishing the relationship of coke deposition as a function of reaction time for the catalyst used to give a coke deposition - time relationship, e. Using the temperature - time relationship of b., the yield - time relationship of c., and the coke deposition - time relationship of d. to calculate a yield - temperature relationship at a given coke deposition percentage. <EOS>