Is there a way to use the compound interest formula, simple interest, or APY to find the price of something years earlier if the price of it was increasing by a certain percentage annually?

  • Yeah, you can solve for any one variable by re-arranging the formulas. A quick search turned up this site which seems to have a working calculator solving for present value: keisan.casio.com/exec/system/1232691482 Note 'nominal' vs 'effective' rate options for APY vs APR.
    – Hart CO
    Commented Apr 16, 2019 at 23:13
  • @HartCO thank you for your assistance, the calculator helped but now I want to work the math on paper. what variable am I needing to re-arrange for compound interest to find this?
    – user30558
    Commented Apr 16, 2019 at 23:25

1 Answer 1


The math is a straightforward rearrangement of the time value of money equation. Just treat the FV amount as the current amount and the PV as the past amount.

PV = FV/{(1+i)^n}

  • i here would be interest rate over 100, not just the number. For ex, 8% interest rate would mean i=0.08 It'd be good to add that clarification. Commented Apr 17, 2019 at 21:46

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