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Type your principal, rate, and term — see the future value, total interest earned, and a year-by-year growth table. Add optional monthly contributions to see what consistent investing does over time.
Future value
$22,196
After 10 years at 8%, compounded monthly.
Principal vs interest
Initial principal
$10,000
Total contributions
$10,000
Future value
$22,196
Compound interest is interest paid on interest already earned. Every period, your balance grows by the interest accrued — and the next period's interest is computed on the larger balance. Over decades, this is what turns small monthly contributions into life-changing balances.
Daily compounding outpaces yearly compounding for the same nominal rate, but the gap is smaller than people think. The biggest lever is time — adding 10 years at 8% beats switching from yearly to daily compounding at the same rate by a wide margin.
The calculator assumes a single nominal annual rate, end-of-period contributions, no taxes, and no inflation. Real returns (after inflation) and after-tax returns are lower. Use this as a directional planning tool, not a guarantee.
Compound interest is interest earned on both the original principal and on the interest accumulated from previous periods. The formula is FV = P × (1 + r/n)^(n × t), where P is the principal, r is the annual nominal rate, n is the number of compounding periods per year, and t is the duration in years. With contributions, an annuity term is added on top.
More frequent compounding earns slightly more for the same nominal rate, but the difference shrinks at higher rates and is dwarfed by time and contribution size. For example, $10,000 at 8% over 10 years grows to $21,589 with yearly compounding versus $22,254 with daily compounding — a 3% gap. Time matters far more: the same investment over 30 years multiplies by roughly 10×.
A quick mental approximation: divide 72 by the annual interest rate to estimate how many years it takes for an investment to double. At 8%, money doubles roughly every 9 years. At 12%, every 6 years. It's not exact, but it's accurate enough for back-of-the-envelope planning.
No. The displayed future value is in nominal terms — the same currency units you're entering today. To estimate purchasing power, subtract a rough inflation rate from your expected return rate before running the calculation. For example, an 8% nominal return at 3% inflation is roughly a 5% real return.
No. The calculator is educational only — it assumes a constant rate, no taxes, and no fees. Real-world investment returns vary year to year, are taxed depending on jurisdiction and account type, and may incur platform or fund expense ratios. Consult a licensed financial planner for actual planning.
Investing monthly instead of a single lump sum? Try the SIP calculator.
For information only — not financial, tax, or legal advice.
Compound-interest results assume a constant nominal rate and end-of-period contributions. Real-world returns vary, are taxed, and may incur fund or platform fees. Always verify with an official source and a licensed professional before filing, borrowing, or transacting. Read the full disclaimer.
ExpenseFlow logs your contributions as recurring transactions and shows your portfolio next to your real budget — the full picture in one workspace.
