<prompt> Human: I made a thread a few days ago asking about this. People rightfully put me in my place on a few things, and I re-evaluated my budget quite a bit. But, Im still hung up on this 30 thing, and why people put so much faith in it when it lacks all sorts of case-by-case context.Im looking for my first big-kid job after a number of years working for less than minimum wage a glorified internship, you could say. There, I spent about 32 of my income on rent and had a surplus of 750 per month a cheap place to live thankfully. With the salary of the jobs Im looking for in a different city, all the math Im doing suggests I could spend as much as 45 on rent and have an even larger surplus of 1300.Being as that I only really spend 500 of my current surplus on myself including food, utilities, entertainment, etc I see it as an upgrade. Here, I save 250 a month, which isnt much but its something. Living the same lifestyle my own apartment, no roommates with this other job, Id theoretically be saving 800 a month.With that said, I dont quite understand the foundation of the 30 rule, and why scale and lifestyles arent considered.Somebody spending 50 on rent making 50k will have a higher surplus than somebody spending 25 and making 25k. Their taxes will be higher, so its not nearly as significant as it seems at first glance, but the surplus is higher nonetheless. Its not like food is twice as expensive, or that youll buy two new laptops nstead of one, if you make twice as much money. Somebody who makes a million dollars a year can still live off 150 worth of food a month, if they really want to.The only thing I see the rule being important for is for establishing your emergency fund: the higher your rent, the more money youll need set aside, but I feel like that can have a cap and that skimping on quality living can do more harm than good.So why, specifically, do they say 30? Why not 40, or even 50, if your lifestyle is such that the scale of your income can still support your needs and goals? The number just seems so arbitrary to me. Some people spend 40 of their income on booze, cigarettes, fast food, entertainment, transportation, and all sorts of other stuff that doesnt come in to play for my lifestyle. So if I can bikewalk to work, cook for myself, avoid unnecessary expenses, and stay entertained with little more than an internet connection, is there anything inherently wrong with using a 45 rule instead of a 30 rule?I understand that its WISE to save as much money as possible, but why does the rule make it sound like its required?  <response>: Rule of thumbs arent precise they are just rough ideas. 