Compound Interest Calculator
Calculate compound interest, future value of investments, and savings growth
Investment Details
Quick Scenarios
Investment Growth Results
Investment Summary
Investment Composition
Year-by-Year Growth
| Year | Starting Balance | Contributions | Interest | Ending Balance |
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How we calculated this
Year-by-Year Growth
What if?
Each row recalculates with your current inputs. Tap a row to apply it.
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Fill in your initial investment, contributions, and return rate above
Authoritative sources and references
The official standards, guidelines, and research behind this calculator's methodology.
Compound Interest Calculator FAQ
What is the difference between annual and monthly compounding?
Monthly compounding applies interest twelve times a year, so interest starts earning interest sooner. Over long periods, more frequent compounding produces noticeably higher returns than annual compounding at the same nominal rate.
How do I include regular monthly contributions?
Enter the contribution amount and choose monthly frequency. The calculator adds each deposit at the start or end of the period you select and compounds it together with your principal.
Does the calculator account for taxes and inflation?
No. Results show gross compound growth. For real-world planning, compare the final amount against expected inflation, and check whether your interest is taxable in your jurisdiction.
What is the Rule of 72?
Divide 72 by your annual return rate to estimate doubling time: at 6%, money doubles in about 12 years (72 ÷ 6), at 9% in about 8. The rule is an approximation that is accurate between about 4% and 12% and this calculator gives you the exact figure.
How much difference does starting 10 years earlier make?
Investing $200/month at 7% from age 25 to 65 yields about $525,000, while starting at 35 yields about $244,000 — the first decade contributes only $24,000 of principal but roughly doubles the outcome. Compounding time is the single most powerful variable you control.
What annual return should I use in the calculator?
For long-horizon global equities, many planners model around 7% nominal (about 5% after inflation) based on long-run historical averages; balanced portfolios and savings accounts run lower. Model a range of rates rather than one optimistic number — the downside case is the one your plan must survive.
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