Getting your fiduciary house in order is challenging enough without bringing complicated arithmetic into the equation (so to speak). Fortunately, nerds across the Internet have programmed useful tools that will do the dirty work. Not sure if you can afford a mortgage? Want to know how quickly you can pay off you credit card? Punch in a few numbers and the following sites will provide the answers you need.

Mortgage tools

What you're calculating: Mortgage payments (for beginners)
For those at the very early stages of the home buying process or who are wondering if a purchase is even feasible, this is a quick and dirty first step to estimating a mortgage, and it takes about five seconds (no lie). Enter the price of the desired property, the percentage of the intended down payment and an interest rate for the loan (the site provides a default average); the site will spit out a monthly mortgage payment, along with useful tips on property taxes and other hidden fees.

What you're calculating: Mortgage payments (for the financially savvy)
All mortgages are not created equal. They are simply loans whose structure and terms can be dickered with in various ways. Those who didn't flunk out of econ might wonder, say, whether they're better off with a 15-year loan at a 5 percent rate, or a 30-year loan at 6 percent. This comparison calculator will work out the relative merits and costs of different loan options, including fancy bar graphs of monthly costs and savings for each.

What you're calculating: Mortgage affordability
Qualifying for a mortgage is no guarantee. The bank has to feel like you're worth the risk (a much more challenging proposition since banks have taken a bath on shaky housing loans in the past year). Granted, there are ways to make your case stronger, but mostly banks play by a set of fairly cookie-cutter rules, based on your income, existing debt and a few other factors. This calculator will let you know, after asking the size of the mortgage you're seeking and some other details, whether your income is high enough to merit consideration. And its handy bar graph lets you know how the outlook changes at different interest rates.

What you're calculating: Whether to rent or buy
Renting or buying is a personal choice that can't really be boiled down to simple math. But if you're cool with the idea of an inanimate computer making important decisions in your life, you could do worse than this tool from Bankrate.com. After asking some basic questions about your financial history, it gives stock advice about what might be the best way to go.

What you're calculating: Payment acceleration
On a typical $100,000 mortgage, you could save $10,000 by increasing your monthly payment by as little as $20. If this sounds appealing, consult this mortgage-acceleration analyzer, which will tell you what you stand to gain by adjusting your payments just a skosh.

Other financial tools

What you're calculating: Debt repayment
Whether it's student loans, a credit card or unfriendly loan sharks, anything you owe at a sharp interest rate (or even a modest one) is something you probably want to get rid of in the near future. Try using the payoff-goal calculator, which computes how much you need to shell out each month in order to get rid of the IOUs by a target date.

What you're calculating: Necessary retirement savings
You might be living it up on David Chang's latest pork candy now, but it will be all ramen and Fancy Feast if you don't give at least some thought to retirement. At the risk of sounding like your cranky uncle, it's never too early to start preparing. This retirement calculator will help put you on the right track. After crunching two pages’ worth of data about your wages, benefits, pensions, projections, investments and savings, this site yields tips on shaping your financial plans in order to reach your retirement goals.

What you're calculating: Whether to lease or buy a car
Sick of public transportation? If you're resolved to wrestle with the burden of owning a car in the city, next you have to wrestle with the decision of how to finance it. This auto calculator, from the personal-finance gurus at Kiplinger's, shows you a straight-up side-by-side comparison of both options: average cost per year, monthly payments, and interest and depreciation expenses.

What you're calculating: Becoming a millionaire
All the aforementioned cash-management headaches would be moot if you were just, you know, rich. If you are patient and disciplined, it's probably within your reach (even for the non-hedge-funders among us). Trust us that this millionaire calculator will get you a lot closer to that goal than Ed McMahon. It computes what exactly it will take to reach the magic number by your desired age. (Let's hope it's not 30.)