Simple Savings Calculator - Future Value and Interest

The simple savings calculator projects the future value of cash that starts with an opening deposit and then receives a monthly transfer, with interest compounded monthly. Despite the word “simple” in the name, the math is compound interest, not the I = Prt simple-interest formula. Households use it for a first-pass emergency fund, a vacation sinking pile, or a cash bucket that should not be confused with a brokerage backtest. The annual rate becomes r = i/12 and the year count becomes n = years × 12. Future value of the opening amount is PV × (1+r)^n. Future value of monthly savings is PMT × ((1+r)^n − 1)/r, or PMT × n if the rate is zero. Deposits are treated as end-of-month, which matches a payday transfer that lands after interest is posted. Banks that compound daily or credit quarterly will print a slightly different statement. Set monthly savings to zero to see what a lump sum does on its own. Set the opening amount to zero to see only the contribution stream. That split is handy when you are deciding whether to dump a bonus in now or raise the monthly automatic transfer. Taxes on interest, account fees, and inflation are omitted, so the figure is a nominal balance, not spending power. Do not paste a promotional three-month APY into a ten-year run. Variable rates, step-up accounts, and early-withdrawal penalties sit outside the model. Keep one currency, run a conservative rate and an optimistic rate, and treat the simple savings calculator as an educational projection rather than a guaranteed bank balance or investment advice. If the account has a monthly fee, subtract twelve times that fee from each year’s ending balance in a side note, because the formula does not deduct costs. A two-rate comparison—today’s APY versus a 1% lower stress case—usually teaches more than a single optimistic run.