finance calculator

Compound Interest Calculator

Estimate compound growth, present value, required rate, required time, and growth with recurring contributions.

Illustration only. Returns are not guaranteed.

Estimated result

Enter assumptions and choose Calculate.

Formula version 1.0.0 · Contributions occur at period end.

Compound growth model

Compound interest formulas

For principal P, annual rate r, m compounding periods per year, and t years: FV=P(1+r/m)^(mt).

Present value

PV=FV/(1+r/m)^(mt).

Recurring contributions

End-of-period contributions C add C((1+i)^n−1)/i. At zero rate they add Cn.

Reverse calculations

The calculator can solve for required annual rate or time using roots and logarithms when the inputs define a valid growth scenario.

Important limitations

Results exclude taxes, product fees, inflation, changing rates, and market volatility. They are not a return guarantee or financial advice.

How to use this calculator

Choose Future value, Present value, Required rate, Required time, or Growth with contributions.
Enter every displayed amount, annual percentage rate, years, and compounding frequency.
For recurring growth, enter the end-of-period contribution.
Select Calculate and review the result, contribution total, growth, steps, and assumptions.

Symbols and units

Symbol	Meaning	Unit or domain
`P`	Starting principal	One consistent currency
`FV`	Future value	Same currency as P
`r`	Nominal annual rate	Decimal rate
`m`	Compounding periods per year	Positive integer count
`t`	Time	Years
`C`	End-of-period contribution	Same currency as P

Checked examples

Annual compound growth

Inputs: Principal 1,000; rate 5%; 10 years; 1 compound/year

Calculation: 1,000×(1+.05)^10

Result: Approximately 1,628.89

Growth before fees, taxes and inflation is approximately 628.89.

Check: compound-interest.test.ts — calculates future value

Zero-rate contributions

Inputs: Principal 500; contribution 100; 2 years; 12 periods/year; rate 0%

Calculation: 500 + 100×24

Result: 2,900

With no growth, future value equals principal plus contributions.

Check: compound-interest.test.ts — handles zero-rate recurring contributions

Assumptions, rounding, and limits

Constant nominal annual rate and fixed compounding frequency.
Recurring contributions occur at each period end.
One currency is used throughout; no currency conversion occurs.
Taxes, fees, inflation, changing returns and market volatility are excluded.
Displayed currency values round half-up to two decimals; formula calculations retain working precision.
Illustrative estimate only; returns are not guaranteed.

Frequently asked questions

Are contributions made at the start or end of a period?

This implementation models end-of-period contributions.

Does the result include inflation, tax or fees?

No. Those effects must be assessed separately.

Can the calculator solve for rate or time?

Yes when positive inputs define a mathematically valid growth scenario.

Sources and review

OpenStax: Compound Interest — Section 6.4; accessed 2026-10-25
U.S. Securities and Exchange Commission: Compound Interest Calculator — Investor.gov calculator guidance; accessed 2026-10-25

Formula version: compound.interest@1.0.0
Formula review: Equatara formula review
Editorial review: Equatara editorial review
Last verified: 2026-10-25
Applicability: Global mathematical growth illustration; not investment advice or a return forecast.
Next review: Domain review by 2027-04-25 or on material change.

Found a problem?

Report a formula, result, example, source, or accessibility issue through the calculator correction process. Do not include sensitive input values.

Calculate compound interest