When it comes to taking out a home loan, the numbers are important. You need to know how much money you have for a down payment, how much you're earning, and how much you can afford to pay in repayments. It's enough to drive you crazy, even with a good pocket calculator! That's where mortgage calculators can be incredibly useful. They can take all the figures you have and turn them into outcomes. You can change one variable (eg size of down payment) and know what effect that will have on your repayment. And a mortgage calculator can do it in the blink of an eye.

Like most things to do with home loans, though, it's not as simple as one mortgage calculator that does one type of calculation. Instead there are numerous different types of mortgage calculators, and some which combine more than one feature. So it helps to know what exactly you want to mortgage calculator to calculate, so you can choose the right one.

Affordability calculator - this type of mortgage calculator basically determines what you can afford. This is based on your current income and expenses. Quite often with this type of calculator you can alter the amount of down payment you will be contributing, and see the effect it has on affordability. Sometimes, if you're a bit close to the wire, putting in slightly more down payment will be enough to make the loan affordable.

Consolidating debt - these calculators look at the various options you have when consolidating debt, and how that will affect your home loan. These options could include: merging non-mortgage debt (i.e. credit cards) into your existing mortgage, refinancing and existing mortgage and paying out a couple of extra debts at the same time, or perhaps a situation where you have both a first and second mortgage on a property and you want to work out the cheapest method of paying the loans out.

Payment calculator - basically, this mortgage calculator works out your monthly payment on a loan. You can use this to determine what effect a change in interest rates might have on your payment, whether you would be paying more or less if you swapped to a fixed rate loan, whether paying fortnightly will make a difference, and so on.

Additional Payment calculator - mostly this is used for determining the effect of a one time lump sum payment, but can also be used to work out the effect of a regular extra payment, say $100 a month. You can adjust almost anything, including amounts, frequency of additional payments and interest rates.

Refinance calculator - this mortgage calculator is mostly used for comparing different mortgages to determine whether refinancing will save you money. This particularly works well if you have more than one mortgage and want to merge them. You can also factor in things like refinancing costs, for example what it will cost to pay out your existing loan. If those costs are very high, it may not be worthwhile refinancing at all.

Amortization calculator - there are two types of amortization mortgage calculators. One works out the savings a borrower makes on his tax based on the interest paid, and the other determines the appreciation of the mortgaged property.

Comparison calculator - this one is handy is you have two very similar mortgages to choose between. Usually you can change different elements of each loan, such as interest rates or payment details, to see the effect. Mostly mortgage brokers use this type of mortgage calculator when making their recommendations.

This is only the tip of the iceberg! There are mortgage calculators for almost anything you can think of in regards to a home loan, but the ones above are certainly the most common. If you visit any of the big lending companies online, such as Freddie Mac or Fannie May, you will be able to visit their interactive pages and do your calculations online. Some other sites even allow you to download a mortgage calculator for free.

The important thing is to let a mortgage calculator do the work for you. There's no point spending hours slaving over your calculator or setting up a spreadsheet, when an online mortgage calculator can do the same thing in seconds.