Save · 2026 rules
Compound Interest Calculator
What a starting balance plus regular contributions becomes over time, with the year-by-year table and how much of the total is growth.
The short answer
What you start with
Contributing at the start of the month buys an extra month of growth each time.
Assumptions
A guess, not a promise. Long-run stock market averages sit near 7% after inflation.
Keeps your saving in step with pay rises.
Balance after 25 years
$462,290.03
You put in $160,000.00. The other $302,290.03 is growth, or 65.4% of the final balance.
Deposits versus growth
Growth starts as a sliver and ends as the larger share. That crossover is the whole point of starting early.
Hover the chart to read any year.
- What you put in
- Growth
Total you contributed
$10,000.00 to start, then $500.00 a month
Total growth
Final balance
In today's money
Adjusted for the current 3.5% inflation rate, so you can compare it with prices you know now.
Balance in today's spending power
Using a real return of 3.50%
Lost to inflation
Inflation figure: Bureau of Labor Statistics, Consumer Price Index, June 2026.
Show the mathThe formula and the year-by-year table
Interest is applied monthly at one twelfth of the annual rate, and each contribution starts earning from the month it lands.
each month: balance = balance × (1 + 0.005833) + 500 monthly rate = 7% ÷ 12 = 0.5833% months = 25 × 12 = 300 final = $462,290.03
| Year | Added | Growth | Balance |
|---|---|---|---|
| 1 | $6,000 | $919 | $16,919 |
| 2 | $6,000 | $1,419 | $24,339 |
| 3 | $6,000 | $1,956 | $32,294 |
| 4 | $6,000 | $2,531 | $40,825 |
| 5 | $6,000 | $3,148 | $49,973 |
| 6 | $6,000 | $3,809 | $59,782 |
| 7 | $6,000 | $4,518 | $70,299 |
| 8 | $6,000 | $5,278 | $81,578 |
| 9 | $6,000 | $6,094 | $93,671 |
| 10 | $6,000 | $6,968 | $106,639 |
| 11 | $6,000 | $7,905 | $120,544 |
| 12 | $6,000 | $8,910 | $135,455 |
| 13 | $6,000 | $9,988 | $151,443 |
| 14 | $6,000 | $11,144 | $168,587 |
| 15 | $6,000 | $12,383 | $186,971 |
| 16 | $6,000 | $13,712 | $206,683 |
| 17 | $6,000 | $15,137 | $227,820 |
| 18 | $6,000 | $16,665 | $250,486 |
| 19 | $6,000 | $18,304 | $274,790 |
| 20 | $6,000 | $20,061 | $300,851 |
| 21 | $6,000 | $21,945 | $328,796 |
| 22 | $6,000 | $23,965 | $358,760 |
| 23 | $6,000 | $26,131 | $390,892 |
| 24 | $6,000 | $28,454 | $425,345 |
| 25 | $6,000 | $30,945 | $462,290 |
Where this is a simplification
Questions
What people ask
What return should I assume?
Nobody knows. A broad stock index has averaged roughly 7% a year above inflation over long periods, but any particular decade can be far better or far worse. Run the calculator two or three times with different rates. The spread between those answers is the honest one.
Why does the growth line start so flat?
Compounding pays on the balance you already have, and early on that balance is small. The curve only bends once growth is earning on previous growth, which is why the last ten years of a long horizon usually add more than the first twenty.
Does this account for inflation?
The main figure does not. It is in future dollars. The panel underneath re-runs the same contributions at a return reduced by the current published inflation rate, which gives you the balance in today's spending power.
Does it include fees or tax?
No. Subtract your fund's expense ratio from the return you enter to account for fees. Tax depends on the account: nothing inside a sheltered account, otherwise tax on dividends and realised gains along the way.
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