Is there an (ideally online) credit card interest calculator that includes grace periods and lets you choose the interest calculation method (eg, "adjusted balance", "average daily balance", "two-cycle average daily balance", and the other methods listed at http://credit.about.com/od/creditcardbasics/tp/finance-charge-calculation.htm)?

Most online interest calculators are much simpler and don't compensate for the complexities of grace periods and interest calculation methods.

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    I don't know why somebody downvoted this, but I've restored balance to the Force. +1. – Chris W. Rea Jan 15 '11 at 13:32
  • Say there exists such a calculator. What are you looking to do with this? What insights are you looking for? – mbhunter Jan 18 '11 at 4:46
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    I want to know how much interest I'll pay in various scenarios, and what changes I can make to avoid paying interest at all. – barrycarter Jan 18 '11 at 18:50
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    Barry - it's simple - pay the balance in full every month. This will avoid all interest charges. – JTP - Apologise to Monica Jan 19 '11 at 1:38
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    OK, but 1) what if I don't pay the full balance in July-- what's the situation for August?, and 2) I want to use the grace period to my advantage, and paying the whole balance monthly isn't always the best deal. Your answer is correct, but not complete. – barrycarter Jan 19 '11 at 2:58

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.


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.


(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.

  • But, what if I'm looking to reduce or minimize my interest payments in situations where I can't or haven't not-used the card for a full billing cycle? – barrycarter May 2 '11 at 16:33

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