Compound Interest Calculator
Calculate compound interest with year-by-year breakdown — enter principal, rate, period, and monthly contributions. Free online compound interest calculator.
Updated April 2026
Advanced options
Breakdown
| Year | Balance | Period interest | Invested |
|---|---|---|---|
| 1 | $627,027.93 | $27,026.93 | $600,001.00 |
| 2 | $1,316,757.55 | $89,729.62 | $1,200,001.00 |
| 3 | $2,075,460.14 | $158,702.59 | $1,800,001.00 |
| 4 | $2,910,032.98 | $234,572.84 | $2,400,001.00 |
| 5 | $3,828,063.11 | $318,030.13 | $3,000,001.00 |
| 6 | $4,837,896.26 | $409,833.14 | $3,600,001.00 |
| 7 | $5,948,712.71 | $510,816.46 | $4,200,001.00 |
| 8 | $7,170,610.81 | $621,898.10 | $4,800,001.00 |
| 9 | $8,514,698.73 | $744,087.91 | $5,400,001.00 |
| 10 | $9,993,195.43 | $878,496.70 | $6,000,001.00 |
How to use the compound interest calculator
Four fields, a full year-by-year breakdown
1. Enter principal, rate, and time period
Starting amount, expected annual interest rate, and how many years (or months) the investment will grow.
2. Add contributions and compounding frequency
Optional monthly contribution, plus annual, semi-annual, quarterly, monthly, or daily compounding — even one-time or recurring extra deposits.
3. Read the year-by-year table and chart
Balance, accumulated interest, and total contributed, updated instantly with a scrollable table and growth chart.
What this compound interest calculator does
A full breakdown, not just a final number
Scrollable year-by-year (or month-by-month) table
Watch the balance grow at every single period, not just at the end of the term.
5 compounding frequencies
Annual, semi-annual, quarterly, monthly, and daily — compare how much each one actually changes the outcome.
Recurring and one-time extra contributions
Layer a yearly bonus or a specific lump-sum deposit on top of your regular monthly contribution, and stop contributions after a chosen year.
Inflation and tax adjustments
See the net balance after tax and the inflation-adjusted real value, alongside the raw compounded total.
100% in your browser
Every calculation runs instantly on your device — no financial data is ever sent to a server.
How compounding frequency changes the result
$10,000 at 7% annual interest for 10 years, no extra contributions
When you'll reach for this calculator
The most common scenarios among people who use this tool
Retirement planning
Model how much to save each month to hit a target balance, with the exact year-by-year trajectory to get there.
Emergency fund and savings goals
Work out exactly when a fixed monthly deposit reaches a specific savings target.
Comparing investment options
Run the same principal at different rates (4%, 6%, 8%, 10%) to see the real gap over 20–30 years.
Teaching or learning compound growth
The year-by-year table turns the abstract idea of compounding into something you can point at and verify.
Common mistakes
Overestimating the effect of compounding frequency
Switching from annual to monthly compounding adds about $425 over 10 years — far less than extending the time period by 10 years (~$19,000).
Using an overly optimistic rate for planning
For conservative planning, use 5–6% instead of the often-cited 7% historical average for broad index funds.
Forgetting the formula assumes a constant rate
Real returns fluctuate year to year — use the results for comparison and planning, not as an exact forecast.
Ignoring taxes and inflation when comparing scenarios
The headline final balance can look very different from the net balance after tax or the real, inflation-adjusted value — check both before making a decision.
Why use this compound interest calculator
The scrollable year-by-year table turns the abstract formula A = P×(1+r/n)^(nt) into a concrete breakdown you can check period by period, backed by an interactive chart of balance versus contributions.
It supports recurring and one-time extra contributions compounded correctly — each deposit earns interest from the moment it's made — plus optional inflation and tax adjustments, all calculated locally in your browser.
Simple interest vs. compound interest
A gap that widens with time
Frequently asked questions
Simple interest is calculated only on the original principal — $10,000 at 7% for 10 years earns $7,000. Compound interest earns on the principal AND the accumulated interest — the same investment with monthly compounding grows to roughly $20,097.
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