Calculation method
Convert the selected nominal annual rate and compounding frequency, or effective annual return, into an equivalent monthly growth rate. Apply each monthly contribution at the selected start or end of the month.
Investing · General formulas
Compound Interest Calculator
Project how an initial balance and monthly contributions may grow. Use the example values or enter your own numbers to explore an estimate.
Currency formatting only—not an exchange-rate conversion. No country-specific tax or government rules are applied.
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The PDF includes active input values and option labels, results, sources, model assumptions, and the schedule when available. Schedule periods follow the model: years, months, or actual payments.
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Links include eligible rate, term or frequency assumptions only. Dollar amounts are never included. Recipients must enter their own amounts; the link will not reproduce your full financial scenario.
Assumptions & limits
- Interest rate remains constant.
- No taxes, fees, or inflation adjustments.
- Basis: User-entered values.
- Basis: Standard fixed-payment and time-value-of-money formulas.
Source/rule review year: Not applicable — general mathematical model.
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Compound interest, explained Want the mechanics before comparing scenarios?
Compare like with like
A nominal annual rate is not the same as an effective annual return. With nominal rate r compounded m times per year, the equivalent effective annual rate is (1 + r / m)m − 1. For example, 6% nominal compounded monthly is about 6.17% effective for a year before fees, taxes, or inflation.
Contribution and withdrawal timing also matters: end-of-month deposits miss that month’s growth, while a beginning-of-period deposit earns for the full period. Compare tools only after matching the rate convention, compounding period, contribution timing, and fees; a displayed equivalent does not make distinct models identical.
Read the compound-interest guide