Compound Interest Calculator
See how your money grows over time with the live Federal Reserve rate pre-filled automatically.
Rate data sourced from FRED® API — Updated: April 4, 2026
Investment Details
Final Balance
$28,832
Interest Earned
$6,832
Total Contributions
$22,000
Rule of 72: Your money doubles every ~19.8 years
At 3.64% annual interest, divide 72 by your rate to estimate doubling time. This is a quick mental math shortcut used by investors worldwide.
Balance Breakdown
Key Milestones
Year-by-Year Breakdown
| Year | Balance | Interest This Year | Total Interest | Total Contributed |
|---|---|---|---|---|
| 1 | $11,590 | $390 | $390 | $11,200 |
| 2 | $13,240 | $449 | $840 | $12,400 |
| 3 | $14,950 | $510 | $1,350 | $13,600 |
| 4 | $16,723 | $574 | $1,923 | $14,800 |
| 5 | $18,563 | $639 | $2,563 | $16,000 |
| 6 | $20,470 | $707 | $3,270 | $17,200 |
| 7 | $22,448 | $778 | $4,048 | $18,400 |
| 8 | $24,499 | $851 | $4,899 | $19,600 |
| 9 | $26,626 | $927 | $5,826 | $20,800 |
| 10 | $28,832 | $1,006 | $6,832 | $22,000 |
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Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both your initial principal and the accumulated interest from previous periods. Unlike simple interest which only earns on your original deposit, compound interest grows exponentially — you earn interest on your interest. This is why Albert Einstein reportedly called it the eighth wonder of the world.
What is the compound interest formula?
The standard formula is A = P(1 + r/n)^(nt), where A is your final amount, P is your starting principal, r is the annual interest rate as a decimal, n is the number of compounding periods per year, and t is time in years. This calculator uses this exact formula, enhanced to include regular monthly contributions.
What is the current Federal Reserve interest rate?
The current Federal Funds Rate is 3.64% as of April 4, 2026, according to the Federal Reserve via the FRED® API. This rate influences savings account rates, CD rates, and many other financial products. It is automatically pre-filled in the calculator above.
What is the Rule of 72?
The Rule of 72 is a quick mental math formula for estimating how long it takes to double your money. Simply divide 72 by your annual interest rate. At 6%, your money doubles in about 12 years. At 8%, about 9 years. At 10%, about 7.2 years. This calculator displays your personal Rule of 72 result automatically based on your entered rate.
How often should interest compound for maximum growth?
More frequent compounding produces slightly higher returns. Daily compounding earns marginally more than monthly, which earns more than quarterly or annually. However, the difference between daily and monthly compounding is very small. The most important factors are your interest rate, how much you contribute regularly, and how long you invest.
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