Compound Interest & Finance Calculator

By MoneyBees

Full TVM solver — solve for Future Value, Starting Amount, Payment, Years, or Required Return. Includes payment timing, compounding frequency, and inflation adjustment.

Frequently asked questions

What does the compound interest calculator do?

It's a 5-variable Time Value of Money solver. Given any four of Future Value, Starting Amount, Payment, Years, or Required Return, it solves for the fifth — using the standard TVM equation banks and financial calculators use.

How do I calculate how much I need to save monthly to retire?

Pick 'Periodic Payment' as the solve-for variable, enter your target Future Value (e.g., S$1,000,000), Starting Amount, Years until retirement, and expected Annual Return. The calculator returns the monthly contribution needed.

What's the difference between end-of-period and beginning-of-period?

End-of-period (default) assumes you deposit your contribution after interest is applied each month. Beginning-of-period assumes you deposit first, then interest is applied. Beginning gives slightly higher results because each contribution earns one extra period of interest.

Does this calculator account for inflation?

Yes, optionally. Toggle 'Adjust for inflation' and we use the real return formula: real = (1 + nominal) / (1 + inflation) − 1. All dollar values then display in today's purchasing power.

What is compound interest in simple terms?

It's earning interest on your interest. Each period your balance grows, and the next period's interest is calculated on that larger balance — so growth accelerates over time. Simple interest, by contrast, only ever pays on your original amount.

What is the formula for compound interest?

A = P(1 + r/n)^(nt), where A is the final amount, P the principal, r the annual rate (as a decimal), n the number of times it compounds per year, and t the number of years. Add regular contributions and you get the time-value-of-money equation this calculator solves.

What is the Rule of 72?

A quick mental shortcut: divide 72 by your annual return to estimate the years for money to double. At 6% a year, money roughly doubles in 12 years (72 ÷ 6); at 8%, in 9 years. It's an approximation, not exact, but handy for sanity checks.

Does compounding frequency really matter?

A little. More frequent compounding (daily vs annually) gives a slightly higher effective return for the same nominal rate — e.g. 6% compounded daily is about 6.18% effective (APY). The difference grows with the rate but is usually small compared with how much and how long you invest.

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