The best online mortgage calculator. You won’t believe what he can do


THere is an endless supply of online mortgage calculators. Most major personal finance sites have them. The best, in my opinion, is the one you’ve probably never heard of: Karl’s Mortgage Calculator.

You’re probably asking who the hell is Karl? I have absolutely no idea. Well, that’s not quite true. I have e-mailed Karl from time to time. I thought his mortgage calculator was so great I wanted to buy it to add it to my own website. His response was a very polite “no thank you”.

And for good reason. It’s a great calculator. You can find Karl’s mortgage calculator here.

Use our free mortgage calculator to estimate your monthly mortgage payment

Related: Compare mortgage rates online

So what makes this mortgage calculator the best? It is not his appearance. It was built in the 90s (I think). It’s not flashy and sleek like some of the mortgage calculators you find today.

But there are two things I love about it. It’s very easy to use, and there are a ton of options. It’s not just a basic calculator where you paste the amount you are going to borrow and the interest rate and it spits out your monthly mortgage payment.

Yes, it will generate your monthly payments. And it also generates an amortization schedule to show you how your balance will decrease over time.

But it does even more useful things. For example, this allows you to determine how paying extra on your mortgage will reduce your balance, how quickly you’ll be able to pay it off, and how much interest you’ll save. It looks like this:

Prepayment table with regular additional payment of $ 100 / month.

Prepayment data showing how long it will take you to pay off your mortgage now.

Karl’s Mortgage Calculator does a lot more than that. So let’s see the ins and outs of its use.

Calculator options

When you look down at the calculator, you will see a row of buttons. When you click on one of them, it shows more options.


The prepayment option is the one I’m really interested in, especially since my wife and I are thinking about paying off our mortgage. but the calculator has a number of options.

For example, let’s say you have a 30-year mortgage that you’ve had for five years. With a little extra cash, you plan to pay an extra $ 50 per month. How much interest will that save you and when will the mortgage be fully paid off? These questions are easy to answer with this calculation. You can actually put this prepayment into the calculator. Simply click on the “Prepayment” button and add $ 50 in the “Monthly Prepayment” field and the month you will start making this additional payment (eg month 61 of the loan).

Prepayment scenario

Of course, you can change the assumptions to see how different amounts will affect the term of your loan.

But what if you don’t want to pay a little more each month but want to make additional payments every now and then, much like a one-time prepayment? Or what if one month you only pay $ 1,000 more on your mortgage?

Well the calculator has you covered. You can enter this date, including the month in which you will make this one-time advance payment. The calculator will show you how your loan term will be shortened and how much interest you will save.

And Karl, if you happen to read this, well done. For my other readers, this is a great calculator, and I hope you will benefit from it. For my money, this is one of the best mortgage calculators out there – and I’ve looked at a ton of them.

Give it a try and let me know what you think.

Related: Ways to Calculate How Much A Home You Can Afford

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