So you’ve decided to take out a loan. Easy, right? Not quite. The first step is to figure out the type of loan you’re applying for and whether or not it will work for you. Unsecured personal loans, installment loans, balance transfer cards, title loans—there seem to be endless different names for them, but there’s one thing they have in common: they’ll all charge interest. Perhaps the most important part of choosing a loan is knowing how much interest they will charge, and determining how easily you’ll be able to pay it off.

A loan calculator can help you with that. Before you start applying for loans, you can try out different loan lengths and interest rates to see how much you’ll be spending in the long run. The interest can really add up over time, so it’s important to be very aware of your anticipated income and monthly expenses. You’re definitely going to need to set up a budget so you can see how much of a loan you can afford. The last thing you want is to take out more than you can ever afford to pay back and end up in a circle of debt. In addition, a loan calculator can help you see what even small changes in variables (like a one percent difference in an interest rate or borrowing a few hundred dollars less) can mean for your total repayment amount.

Remember, applying for some loans can result in a hard credit check that could lower already-low credit scores. It’s better to already have a good idea of what loan you can afford rather than applying for loans en masse just to see what you’ll get approved for.

It is also important to consider what principal you’ll need. This is the amount of money that you are requesting a lender to give you, You’ll ultimately have to pay back the principal, plus any interest on it that accumulates during the length of your loan. You don’t want to take out more than you need, because you certainly don’t want to pay more interest than you need to. Conversely, if you don’t take out enough, you might have to apply for another loan all over again—you can’t just ask the lender to add a few hundred dollars to the loan later.

Once you’ve decided on your principal and what interest rates you can afford, it’s time to find a loan repayment calculator to suit your needs. You’ll need to know your principal or loan amount, your anticipated interest rate, the loan term (the length of the loan), and how frequent the payments will be.

If you prefer to do your own math, there are formulas out there for you. For most amortized loans, that formula for monthly payments will end up looking something like this:

• A = the monthly payment
• P = the principal, or loan amount
• n = the interest rate
• r = the monthly rate, or n/12. If the loan is repaid with a different frequency, you would change this one accordingly (divide by four for a quarterly payment, for example).

If that equation looks a little overwhelming, try an online loan payment calculator! It’s also a good idea to double-check your math a payment calculator just in case—human error is real.

As you can see, this is a much simpler approach. Try out a few combinations of numbers, and you’ll soon have a better understanding of what an ideal loan for you might be. Armed with that knowledge, you can shop around with confidence.

Of course, these are loan interest calculators for loans with set payments over a fixed amount of time. If credit card debt is what you’re facing, you might want to look into different calculation tools. After all, if you make substantial payments toward your credit card bills, you could drastically reduce the amount of interest you pay on them.

If you prefer to see your payment schedule over time in spreadsheet form, you can hop on Excel or Google Sheets and make your own loan calculator, or even use an existing payment template. Using these tools might help you get a better understanding of what your monthly payments will really look like and could help you track the progress you’re making on your loan repayment so it doesn’t feel like a never-ending task.