My favorite paper on this matter is: https://www.researchgate.net/publication/247925262_Large_Limits_to_Software_Estimation https://www.researchgate.net/publica

My favorite paper on this matter is: https://www.researchgate.net/publication/247925262_Large_Limits_to_Software_Estimation https://www.researchgate.net/publication/247925262_Large_Lim... A crude tldr is: writing software is solving a math problem and time estimating how long it will take to solve a math problem has an infinite error bar.