>>>Hi everybody,
>>>
>>>If I have an item which cost $100 and the annual interest rate is 2% and the days of interest 10, how can I calculate the actual interest cost?
>>>
>>>Can you give me the exact formula, please?
>>>
>>>Thanks.
>>
>>I believe, it depends on the method of calculation and definition of "annual interest rate", that partucular party is using.
>>If it is a credit card, and you are getting bill by ordinary mail, then usually description is printed there. Having description you may derive a formula.
>
>It's an interest rate on a boat - I don't have any more information here, so I wanted to see the most general term.

Simple interest or compound interest? Fixed rate or variable?

Start here:
http://www.discoverboating.com/buying/financing/loancalculator.aspx