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United States compound interest calculator

Project how savings or investments can grow with compound interest and optional regular contributions. Choose monthly, quarterly, or annual compounding to match your account.

Currency USD · Locale en-US · Figures formatted for United States

Added each compounding period.

Results

Future value
$17,175.24
Total contributions
$13,000.00
Interest earned
$4,175.24

How this calculator works

  • Starting balance grows at the chosen compounding frequency.
  • Regular contributions are added each period (end of period by default).
  • Total interest = future value − (starting balance + all contributions).
  • Taxes, fees, and inflation are not deducted.

FV = P(1+r)^n + PMT × ((1+r)^n − 1) / r, where r is the rate per period and n is the number of periods. If r = 0, FV = P + PMT × n.

Worked example

Save 100 per month for 1 year at 12% annual interest, compounded monthly, starting from zero.

Inputs

  • Principal0
  • Contribution100 / month
  • Rate12%
  • Years1

Results

  • Future value≈ 1,268.25
  • Contributions1,200
  • Interest earned≈ 68.25

Frequently asked questions

What compounding frequency should I pick?

Match your product: many savings accounts compound monthly; some bonds annually. If unsure, monthly is a common default for cash savings.

Are contributions at the start or end of each period?

This calculator defaults to end-of-period contributions (ordinary annuity). Beginning-of-period deposits earn slightly more interest.

Does this account for tax on interest?

No. Tax treatment varies by country and account type (e.g. ISA, 401(k), TFSA). Use after-tax rates only if you already know them.

Can returns go down?

This model assumes a constant positive rate. Investment markets can fall; treat the result as an illustration, not a forecast.

Sources and disclaimer

  • Compound interest and ordinary annuity future-value formulas

Estimates only — not financial advice. Results ignore fees, taxes on interest, early repayment charges, and product-specific rules. Verify with your lender or a qualified adviser.

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