Calculate how your money grows over time with compound interest. Compare daily, monthly, quarterly, and annual compounding frequencies.
Compound interest earns interest on both principal and accumulated interest. Formula: A = P(1 + r/n)^(nt). Example: $10,000 at 7% annually for 10 years grows to $19,672. The more frequent the compounding, the higher the returns.
Try an example:
Final Balance
$54,714
Total Interest
$20,714
Total Contributions
$34,000
Effective Annual Rate
7.23%
Growth Multiple
5.47x
Breakdown
Formula Used
A = P(1 + r/n)^(nt) + PMT * ((1 + r/n)^(nt) - 1) / (r/n)Where P = $10,000, r = 7%, n = monthly, t = 10 years
| Year | Interest | Balance |
|---|---|---|
| 1 | +$801 | $13,201 |
| 2 | +$1,033 | $16,634 |
| 3 | +$1,281 | $20,315 |
| 4 | +$1,547 | $24,262 |
| 5 | +$1,832 | $28,495 |
| 6 | +$2,138 | $33,033 |
| 7 | +$2,466 | $37,900 |
| 8 | +$2,818 | $43,118 |
| 9 | +$3,196 | $48,714 |
| 10 | +$3,600 | $54,714 |
Compound interest is often called the "eighth wonder of the world" - a quote attributed to Einstein. Unlike simple interest, which only applies to the original principal, compound interest calculates interest on both the principal and accumulated interest. Per Investopedia, this exponential growth mechanism is the foundation of long-term wealth building.
The power of compounding becomes dramatic over long time horizons. $10,000 invested at 7% for 10 years grows to $19,672 - but over 30 years it becomes $76,123. The same investment over 40 years reaches $149,745. This is why financial advisors emphasize starting to save early. Time is the most powerful variable in the compound interest formula.
For investors and business owners, understanding compound growth is essential for evaluating investments, comparing savings accounts, and planning for retirement. Combine this knowledge with ROI calculations to assess which investments deliver the best returns over your time horizon.
A = P(1 + r/n)^(nt)
With regular contributions:
A = P(1 + r/n)^(nt) + PMT x ((1 + r/n)^(nt) - 1) / (r/n)
Your initial investment or deposit amount. This is the foundation on which all interest is calculated.
The nominal annual rate expressed as a decimal. 7% becomes 0.07 in calculations.
How often interest is calculated and added: daily (365), monthly (12), quarterly (4), or annually (1).
The total investment period. Longer time dramatically increases final results due to exponential growth.
Quick estimate for doubling time: divide 72 by your interest rate. At 7% interest: 72 / 7 = 10.3 years to double. At 12%: 72 / 12 = 6 years. This rule works best for rates between 6-10%. For income from investments you plan to grow, also track dividend yield alongside compounding to understand total return.
A 25-year-old starts investing $500/month in a retirement account earning 7% annually.
Over 80% of the final balance comes from compound interest, not contributions. Starting 10 years later would result in only $567,000 - less than half.
An emergency fund of $20,000 in a high-yield savings account at 4.5% APY.
Your emergency fund grows nearly 25% while remaining liquid. Compare this to a traditional savings account at 0.5% APY: only $20,506 after 5 years.
Lump sum investment of $50,000 in an S&P 500 index fund with historical 10% average return.
The investment grows nearly 7x over 20 years. Note that stock market returns vary; this example uses long-term historical averages and doesn't account for fees or taxes. To measure the exact annualized rate across different holding periods, use a return on investment calculator.
For more guidance, visit the Planning tools hub and the Valuefy blog.
Pair this tool with the TAM SAM SOM Calculator and the Break Even Calculator to cross-check inputs. For strategic context, read our e-commerce valuation case study and explore the Business Planning tools hub.
Time is the most powerful variable - starting 10 years earlier can more than double your final balance due to exponential growth.
More frequent compounding (daily vs. annually) yields higher returns, but the difference is more significant at higher interest rates.
Regular contributions combined with compounding create powerful wealth-building momentum - even small monthly amounts grow substantially over time. For income-generating assets, combine this with dividend yield analysis to model total returns from both growth and income.
APY (Annual Percentage Yield) reflects true returns including compounding; always compare investments using APY rather than stated APR.
Use the Rule of 72 (72 / interest rate = years to double) for quick mental calculations of investment growth potential.