• sugar_in_your_tea@sh.itjust.worksM
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    6 months ago

    It’s really nice when comparing quotes for buying down a rate, or looking at the impact of additional payments. It’s also incredibly easy to throw together. For anyone interested:

    • payment = PMT(mortage rate/12, mortgage term * 12, -initial principle)
    • interest = (mortgage rate/12) * remaining principle
    • principle payment = payment - interest
    • new principle = prev principle - principle payment

    Throw that into a spreadsheet and drag down. Add a SUM() to figure out total interest paid or whatever. I have a VLOOKUP() to calculate interest for the current year for tax planning purposes, for example.

    Maybe I’ll start an unofficial weekly post about various calculations I have in my spreadsheet. I have something like 30 tabs, so surely something there is interesting to others.