Compound Interest Calculator
See how a starting amount plus steady monthly contributions grow with compound interest over time. Get your future balance, how much you actually contributed, and how much of it is pure growth — with a year-by-year chart.
$441,853
You'd put in $190,000 — and compounding would add another $251,853 on top. That growth is your money working while you sleep.
Final balance
$442k
You contributed
$190k
Interest earned
$252k
Estimates, not financial advice. Real returns vary year to year and aren't guaranteed; this assumes a steady average return, contributions spread evenly, and no taxes or fees. Figures are in future dollars (not adjusted for inflation), so their spending power will be lower than it looks today. A starting point, not a promise.
Balance vs. contributions over time
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Compound interest is one piece. LifeFlow shows your real freedom year, the goals and the life you want now, and how every dollar you invest moves your future — all in one warm, living plan.
Try LifeFlow freeWhat is compound interest?
Compound interestis what happens when your money earns returns — and then those returns start earning returns too. Each year's growth is added to your balance, so the next year grows from a bigger base. Over a few years the effect is modest; over decades it's dramatic. That's why starting early is such an advantage: time is the ingredient compounding needs most.
In this calculator, the gap between the balance line and the contributed line is the interest — the part your money earned on its own, without you adding a dollar.
How it's calculated
Your starting amount grows at the expected annual return, and each monthly contribution is added and grows from the point you make it:
Total contributed is your starting amount plus every deposit; interest earned is the final balance minus that. This uses the same compounding math that powers LifeFlow. Inside the app we go further — modelling each account, debt, and goal on its own, each growing at its own real (after-inflation) rate — so a full in-app projection is richer than this single-rate estimate, and the two won't match number-for-number.
Frequently asked questions
What is compound interest?
Compound interest is the interest you earn on both your original money and on the interest it has already earned. Because each period's growth is added to the balance that grows next period, your money accelerates over time — the longer it compounds, the larger the effect. It's often called "interest on interest."
How is compound interest calculated?
This calculator grows your starting amount at your expected annual return and adds your monthly contributions along the way. In formula terms: future balance = principal × (1 + rate)^years + contributions grown at the same rate. Your total contributed is the starting amount plus every monthly deposit; the interest earned is the final balance minus what you put in.
How often is interest compounded here?
This calculator compounds annually using a steady average return, with monthly contributions added through the year — a clear, close approximation for long-term investing. Real-world accounts may compound daily or monthly and returns vary year to year, so treat the result as a well-grounded estimate, not an exact bank statement.
What return rate should I use?
LifeFlow defaults to ~5% as a conservative real (after-inflation) estimate for a stock-heavy portfolio — the same figure the app uses. Some people cite a higher long-run nominal average like 7%, but that is before inflation, so a matching target would need to be in future dollars. The rate is editable, so try a few to see how sensitive your result is — small differences in return compound into large differences over decades.
This is one number. See your whole picture.
These calculators are snapshots. LifeFlow shows your real freedom year, the goals and the life you want now, and how every dollar moves your future — in one warm, living plan.
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