There are other factors which will play a roll in this. First being accessibility. A few years ago my landlord re-roofed his house. That is fine and dandy, however none of the big trucks could get near the roof to where the laborers could toss the old roof into a dumpster, or to where the new roofing materials could be lifted onto the roof with a forklift (due to trees, gardens, fences, walls, pool and other various things). That problem lead to the roof job costing him $ 8,000 (USD) more. The materials needed - for instance a 'cheap' 20 year asphalt shingle will cost far less than a 50 year asphalt shingle. Spanish tiles handcrafted by the virgins of the San Padre Nunnery in the foots hills of the Peruvian Mountains will cost a bit more than the concrete Faux Spanish tiles factory formed in the next city over from yours. Where you live - what region - will have an impact on the over all costs. Think about half of the cost will be materials, the other half (or slightly more than half) will be labor. Thus if you live in an area where e cost of living is high, the price of that roof will be high. If you live in an area where the cost of living is low, then the price will be low. How much unseen damage can have an impact on the final cost. I have seen simple shingle re-roofing become a total roof structure replacement since the sheathing and the framing beneath were rotted out. It costs a penny or two more to replace roof, framing, and all than just having the shingles replaced. Competition in the roofing industry also has an impact on the price to you. If there are a lot of roofing companies in your area, then getting several estimates may result in getting several very low bids - especially if these companies are hungry for work. If you live in an area with a handful of roofing contractors all of whom are back-logged (with lots of clients) they will be able too afford sticking it to you. Ultimately they know that you need them, not the other other way around. How much are you willing to do yourself? If you remove the roofing already in place (many areas the code allows the owner to remove the roofing - shingles, tar paper, blah) the final cost may be substantially lower. If you did a search on the net you most likely got a lot of hits where a lot of people have asked the same question (or similar). The reason being is because there is no calculator out there that takes into account all of these various factors. Give all of these factors, and the input of your Square footage (without location, what kind of roof, the skill and number of roofers on the job) it can range from $2.000.00 to $12,000.00. Yes that is a large range there - but then there is a lot of unknowns.