Most people are used to typing their numbers into boxes with familiar features. But don't be dazzled only by the graph, boxes are still available further down the page so that you can use numbers instead of the scales. Using Karl Jeacle's mortgage calculator against one on a different website can give you different a different feel for what looks like the same set of figures.

It's all to do with the basic programming that has developed around mortgage calculator. Some mortgage calculators are very basic, they input very simple basic numbers and a few calculations take place in the program behind the scenes on your computer. They give you suggested figures that, although not perhaps 100% accurate, will give an approximate idea of what the property will cost you.

There are other factors that need to be taken into account when a mortgage is computed, such as your age and state of health for example. Many basic mortgage calculators won't take this into account, but some more sophisticated programs can. These will give a more accurate analysis of the mortgage situation you would face as it will have more information about you personally. The more the mortgage calculator knows about you, and the property, the more detailed and accurate the answers it gives will be.

This is another reason why sliding scales such as Karl Jeacle's Graphing calculator might not work for some people. Sliding scales are often better for approximation rather than specific numbers. Perhaps 48 instead of 50 is "almost" right, but it's not going to create the most accurate analysis and the hard figures you need to figure out your budget and finances. The various colors on this mortgage calculator are also a little less clear than straight forward numbers.

So why even mention Karl Jeacle's mortgage calculator? Even though it won't give you precise numbers, and no calculator does, the graphics give you a feel for just how much that mortgage is really costing you. You can see for yourself, graphically, how adding a little bit to your monthly mortgage payment makes a large difference down the road.

Using a variety of different mortgage calculators gives you a good overall feel for how a mortgage on a particular property would affect your budget.

But, make sure that you know what their figures are based on. For example, the mortgage calculator may not ask you for a mortgage term, but somewhere on the calculator site there may be a note to say that calculations are based on 30 year mortgages.

The same could be true about interest rates. While some mortgage calculators ask you to input the interest rate, others assume an "approximate" rate. Mortgage calculators linked to specific lenders could take the interest rate automatically from the lenders financial pages so they are the current default rate and not able to be altered even if you have perfect credit.

Use one calculator at first to pin down your basic options and figures. Then test those numbers out on a variety of mortgage calculators to get the best feel for how your new mortgage will affect your finances and change your life.