Credit card interest calculator with grace period & different interest rate calculation methods?
I thought it was such a useful suggestion that I went ahead and created them. I'm sure you're not the only one who could derive some benefit from them, I know I will. http://www.investy.com/tools When I have some additional time, I will add the option for grace-periods, but for now I wanted to get them up so you could use the calculations as-is from the article. Enjoy. (Disclosure: I'm the founder of the site they are hosted on and I wrote the code for the calculators) If you want to ensure that you stop paying interest, the best thing to do is to not use the card for a full billing cycle.  Calculating credit card interest with precision ahead of time is difficult, as how you use the card both in terms of how much and when is critical.
The statement in Wikipedia is generic. Whether a particular Bank would charge as per above example or not would be in the card holder's agreement.   So if you do not have any dues, and on 10th April you charge $1000, and on 13th April you charge $500. Statement date is 18th April. Grace Period to pay is say 10th May.   If you do not pay in full by 10th May, and say you only pay $500, Bank would charge interest from 19th April to 10th May for $1500, post 10th may they would charge interest for $1000 balance. Further all fresh purchases would be charged interest from day 1. Net Net Morale of the story is do not carry / revolve money on Credit Card. For all practial purposes use a credit card as a convenience card. "So, there is no truly ""correct"" way to calculate return.  Professionals will often calculate many different rates of return depending on what they wish to understand about their portfolio.  However, the two most common ways of calculating multi-period return though are time-weighted return and money-weighted return. I'll leave the details to this good Investopeadia article, but the big picture is time-weighted returns help you understand how the stock performed during the period in question independent of how you invested it it.  Whereas money-weighted return helps you understand how you performed investing in the stock in question.  From your question, it appears both methods would be useful in combination to help you evaluate your portfolio. Both methods should be fairly easy to calculate yourself in a spread sheet, but if you are interested there are plenty of examples of both in google docs on the web." An amortization schedule is often used to produce identical payments for the term (repayment period) of a loan, resulting in the principal being paid off and the debt retired at the end of the loan. This is in contrast to an interest only, or balloon loan. These loans require little or no payment against the balance of the loan, requiring the loan to be paid indefinitely if there is no term, or requiring the loan to be entirely paid off from cash or a new loan at the end of the term. A basic amortization formula can be derived from the compound interest formula:   This formula comes from the Wikipedia article on amortization. The basics of the formula are the periodic payment amount, A (your monthly payment), can be determined by the principal loan, P, the rate, r, and the number of payments, n.  Lenders lend money to make a profit on the interest. They'd like to get back all the money they lent out. Amortization schedules are popular because the fixed low payments make it easier for borrowers to pay the loan off eventually. They also tend to be very profitable for lenders, especially at the start of the term, because they make a lot of profit on interest, just like the start of your mortgage. The principal of a mortgage has more meaning than the principal of a revolving debt credit card. The mortgage principal is fixed at the start, and represents the value of the collateral property that is your home. You could consider the amount of principal paid to be the percentage of your home that you actually own (as part of your net worth calculation).  A credit card has a new balance each month depending on how much you charge and how much you pay off. Principal has less meaning in this case, because there is no collateral to compare against, and the balance will change monthly. In this case, the meaning of the amortization schedule on your credit card is how long it will take you to pay off the balance if you stop charging and pay at the proscribed payment level over the term described. Given the high interest rate on credit cards, you may end up paying twice as much for goods in the long run if you follow your lenders schedule. Amortizing loans are common for consumer loans, unless a borrower is seeking out the lowest possible monthly payment. Lenders recognize that people will eventually die, and want to be paid off before that happens. Balloon and interest only bonds and loans are more commonly issued by businesses and governments who are (hopefully) investing in capital improvements that will pay off in the long run. Thousands of people and businesses have gone bankrupt in this financial crisis because their interest only loans reached term, and no one was willing to lend them money anymore to replace their existing loan. "The debt isn't ""paid off"" until you've brought the balance back to zero. If you pay less than the full amount, some goes to pay down the balance and some goes to paying interest on the balance, and you're left with a debt on the account (which you add to if you continue using the card or reduce when you make a payment to the card.) Note that the ""grace period"" in which you can pay off recent charges without paying interest is often available only when you have paid off the card in full... so carrying a balance costs you money on new charges immediately. Check your statements and plan paperwork to see if this applies to you; if it does that's another reason to pay off this debt as quickly as possible. Not to mention that credit card interest rates tend to be moderately obscene." http://www.calcamo.net/loancalculator/simulation/fixed-rate-loan.php5 This website is a calculator only and has some extra features that take into account late payments, paying extra to reduce principal, and has the ability to export amortization table to excel that you could use to keep track of the loan.   If you are looking for a web site to manage and keep track of the whole process, reminder emails, accepting credit card payments, etc.. paybaq.com may be right for you. "The danger of overdrawing the account via the use of a debit card, and the exorbitant fees that can result make me hesitant to use a debit card. The ability to cover all the transactions with one payment is why I use a credit card for these ""debit"" transactions.  Yes there is a risk of a late payment, but that can be easily avoided within the three week grace period. The ability to electronically transfer the money to pay off the card makes this even easier." I haven't used it in years, but look at GnuCash. From the site, one bullet point under Feature Highlights: The contract is not very clear. As much as I can understand it will still help if you make part prepayments. In an Rule 78 or Actuarial method, the schedule is drawn up front and the break-up of interest and principal for each month is calculated ahead. At the beginning both the reducing balance method as well as Actuarial method will give the same schedule.  However in Actuarial method, if you make part prepayments, they get applied to the future principals, the interest are ignored. However the future interests are not reduced. Example: Say your schedule looks something like this; Monthly Payments say 100; Month | Principal | Interest 1 | 10 | 90 2 | 20 | 80 3 | 30 | 70 4 | 40 | 60 5 | 50 | 50 6 | 60 | 40 7 | 70 | 30 8 | 80 | 20 9 | 90 | 10 So lets say you have made 3 payments of 100, in the 4th month if you make 150 [in addition to 100], it would get applied to the principal of 4th, 5th and 6th month. So essentially you would save interest of 4th, 5th and 5th month. It would also reduce the total payments to 6. i.e. you will only have 7th, 8th, 9th due. The next payment you make of 100 will get applied to row 7. The disadvantage of this method over reducing balance is that the interest calculated for rows 7,8,9 don't change compared to reducing balance. However if you prepay in full, the unearned interest is calculated and returned as per the Actuarial Tables.