WalletHub Credit Card Calculator – https://wallethub.com/credit-card-calculator – This is good for calculating how much you’ll pay for something you put on your credit card. When you absolutely have to charge an item, remember your budget. Try to pay it off as soon as possible, but if you can’t this will help you calculate how long it will take you. You can then decide if it’s worth buying it now on credit for 12 to 18 months or saving until you can afford to pay it in less than 4 payments.

They also have an existing debt calculator to help you determine how long it will take you to pay off your current debt, but it is limited at $50,000 and it always calculates to 4 years.