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Prepaying a loan: Shouldn't the interest be recalculated like a shorter loan?
You are expecting, that if you pay off a 30 mortgage after 16 years, you should be charged the same amount of interest as someone who had a 16 year mortgage for the same amount and with the same interest rate. This isn't correct, and here's why: the person with the 16 year mortgage paid it off faster than you. They paid more each month and the size of their loan shrunk faster than yours. After 15 years they had paid off a LOT more than you. You paid a lump sum after 16 years, but at this point, the extra money which they had paid had been in the banks hands for a long time. You caught up with them then, but you had been behind them for all of the previous years. On the other hand, you owed the same amount in each of those years as the person who took out a 30 year mortgage and didn't prepay. Therefore you paid the same amount of interest as this person, not the first person. If you could arrange in advance a loan where you made the same payment as you did for 16 years, then paid the balance in a lump sum, then you would have paid exactly what you did.