Compound Interest Calculator — Monthly Compounding
Monthly compounding credits interest twelve times a year, so each month's growth starts earning on the very next statement. Compounding more often lifts the effective annual yield (APY) above the stated nominal rate — a 7% nominal rate compounded monthly works out to roughly 7.23% APY. This page pre-fills twelve compounding periods per year so you can see how frequent crediting nudges the ending balance higher than a once-a-year credit would.
Compound interest growth estimate
Estimated future value
$145,180.47
- Starting principal
- $10,000
- Total contributions
- $58,000
- Total interest
- $87,180
Where the balance comes from
Estimate using a fixed annual rate. The principal compounds at the frequency you choose; contributions are grown month by month. Taxes, fees, and inflation are not modeled. An estimate of growth, not investment, tax, or financial advice.
What twelve credits a year actually do
With monthly compounding the formula's n is 12, so interest is figured and added twelve times a year. Each credit raises the balance that the next month's interest is calculated on, which is why a 7% nominal rate compounded monthly works out to roughly 7.23% APY — the extra 0.23 point is pure frequency, not a higher headline rate.
That gap looks small in a single year but compounds along with everything else over a long horizon, so the ending balance lands above what annual crediting would produce at the same nominal rate. Monthly is also the natural setting when you pair the principal with a recurring monthly contribution, since deposits and crediting then fall on the same cadence.
Questions
- Why is the APY higher than the rate I entered?
- Because monthly compounding credits interest twelve times a year, each credit starts earning on the next month's interest. That intra-year growth lifts the effective annual yield above the nominal rate — about 7.23% APY from a 7% nominal rate — even though you never changed the rate itself.
- Should I use monthly compounding for a savings or investment estimate?
- Monthly is a reasonable default for many savings accounts and for any plan with monthly contributions, because the deposits and crediting line up. For an asset that credits less often, switch to the annual page so the frequency matches how the real account actually pays.
More ways to use this calculator
Start with the main compound interest calculator or compare the other published scenarios.
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