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how are mortgage payments decided? [duplicate]
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it's easiest to get your payment from the pmt function in excel or google sheets.  so a $100,000 30 year mortgage at 3% looks like this: the basic calculation is pretty simple.  you take the annual interest rate, say 3%, divided by 12, times the existing principal balance: the idea is that borrowers would like to have a predictable payment.  the earlier payments are proportionally more interest than principal than later payments are but that's because there is much more principal outstanding on month 1 than on month 200.
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