How to calculate interest saved on a loan for early payments?

[money_talks]

Anyone know of a easy to use tool online or calculator for the following scenario on a loan: (just an example).

Principal balance: $1,200

Loan Term: 12 months

Payment per month: $100

APR: 10%

I want to know how much money I would save if I make payments early and compare to see if it's worth making those early payments. For example, how much interest would I save if when Month #4 payment is due, instead of making $100, I make a payment of $200. Then in month #5 payment, I make another regular payment of $100.

[user5387]

I'd start by using one of the installment loan calculators you can find via a Google search.

[BigBS]

I use Excel for things like that, but have not found an easy way.  Just start with what I know the payments and balances to be in 1 column/group of columns and then add the same for the options that I want to compare.  Takes some time, but helps me understand the impacts better.

[user5387]

This calculator has a feature where you can specify extra payments.

If you make extra payments, then something has to change in the overall loan -- either the term becomes shorter, or the monthly payments decrease, or the APR goes up.  Presumably only the first of these is of interest.

http://www.bankrate.com/calculators/mortgages/loan-calculator.aspx