Free online compound interest calculator: enter principal, annual rate and term to get future value, total profit and a year-by-year growth table, with regular contributions and a simple interest comparison
Enter principal, annual rate and term to get the future value and total profit from the compound interest formula
Model monthly deposits with monthly compounding, annual top-ups with annual compounding and more
See the simple interest value under the same terms and exactly how much more compounding earns
Estimate years to double with the rule of 72, alongside the precise calculation
Track cumulative contributions, cumulative profit and year-end balance for every year
Everything runs in your browser - no uploads, no sign-up, and nothing is stored
Type the lump sum you start with, e.g. 100000. Enter 0 if you only want to model regular deposits.
Enter the expected annual return (e.g. 5) and the number of years (e.g. 10), or use the quick buttons.
Pick annual, semi-annual, quarterly, monthly or daily compounding, and optionally add a deposit per period.
The result card shows future value, profit, the simple interest comparison and doubling time; the table breaks the growth down by year.
Estimate the portfolio value of a monthly index-fund plan after 10 or 20 years
See how starting early and adding a little more each year changes your retirement pot
Plan for future tuition by working out the principal and monthly deposits required
Compare savings products at different rates and compounding frequencies
Evaluate long-term holding and dividend reinvestment through a compounding lens
Businesses that reinvest profits each year can estimate multi-year growth
FV = P × (1 + r/m)^(m×n), where P is the principal, r the annual rate, m the compounding periods per year and n the years. The key is that each period's interest joins the principal and earns interest next period. With regular deposits A the formula becomes FV = P(1+i)^N + A × ((1+i)^N − 1) ÷ i, where i = r/m and N = m×n.
Simple interest is paid only on the original principal; compound interest is paid on principal plus accumulated interest. At 100,000 and 5%: after 30 years simple interest reaches 250,000 while compounding reaches about 432,194.24 - a difference of roughly 182,194.24. The longer the horizon and the higher the rate, the wider the gap.
Doubling time in years is approximately 72 divided by the annual rate in percent: about 14.4 years at 5%, about 9 years at 8%. The exact value is ln2 ÷ ln(1+r). It shows how raising the rate or extending the horizon accelerates wealth accumulation.
For the same nominal rate, more frequent compounding raises the effective annual rate: EAR = (1+r/m)^m − 1. At a 5% nominal rate, annual compounding gives 5.00% effective, monthly about 5.12% and daily about 5.13%. The effect is modest - time and rate dominate.
| Term | Compound (annual) | Simple | Extra from Compounding |
|---|---|---|---|
| 10 years | $162,889.46 | $150,000.00 | $12,889.46 |
| 20 years | $265,329.77 | $200,000.00 | $65,329.77 |
| 30 years | $432,194.24 | $250,000.00 | $182,194.24 |