Software engineers, when quoting for fixed priced jobs, learn quite quickly to estimate accurately. Software engineers, when pressured by managers to provide l

Software engineers, when quoting for fixed priced jobs, learn quite quickly to estimate accurately. Software engineers, when pressured by managers to provide low estimates and/or to provide estimates quickly, will estimate inaccurately. (It can also be deliberately high as well as low, based on previous experience of having their estimates chopped in half.) Whether you use SP or T-shirt sizes or whatever, somebody is translating that into days because days (and thus dollars) are what matter to the business. If someone asks me for an estimate, I'll give them a range in days/weeks, and they can turn it into whatever nonsense unit they like.