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Prepaying a loan: Shouldn't the interest be recalculated like a shorter loan?
When you pay off a loan early, you pay the remaining principal, and you save all of the remaining interest. So you do save on interest, but it's the interest you would have paid in the future, not the interest you have paid in the past. (Your remaining balance when you pay off the loan only includes the principal, not the projected interest.) Interest is a factor of the amount borrowed, the interest rate and the amount of time you borrow the money. The sooner you repay the money, the less interest you pay. Imagine if you had taken a 30 year loan at 4% interest but were allowed to make no payments until the loan term ended. If you waited 15 years to make your first payment, you wouldn't owe the same money as if you'd made payments every month. No, instead of owing ~$64k, you'd owe ~$182k, because you had borrowed $100k for 15 years (plus the interest due) rather than borrowing a declining sum. So that's why you don't get a refund on interest for previous months. If you had started with a 16 year loan, then you would have been paying more principal every month, and your monthly amount due would have been higher to reflect that. As you paid the principal off faster, the interest each month would drop faster. Paying a huge portion of the principal at the end of the loan is not the same as steadily paying it down in the same time frame. You will pay a lot more interest in the former case, and rightfully so. It might help to consider a credit card payment in comparison. If you run up a balance and pay only the minimum each month, you pay a lot of interest over time, because your principal goes down slowly. If you suddenly pay off your credit card, you don't have to pay any more interest, but you also don't get any interest back for previous months. That's because the interest accrued each month is based on your current balance, just like your mortgage. The minimum payments are calculated differently, but the interest accrued each month uses essentially the same mechanism.