Compound Interest & Investment Growth Simulator
Model your path to financial freedom. Simulate compound growth trajectories, regular monthly savings, and flexible interest compounding frequencies with exponential custom area charts.
Initial Deposit & Schedule
🔄 Compounding Frequency
Select the compound growth calculation cycle
$120,156
Accrued balance after 15 years compounding at 8% annual yield.
Initial seed + ongoing deposits
Earned entirely from compound returns
Exponential Growth Path Chart
📋 Year-by-Year Growth Table
Chronological wealth projection timeline
| Year | Deposits ($) | Interest Accrued ($) | Net Worth ($) |
|---|---|---|---|
| Yr 0 | $10,000 | +$0 | $10,000 |
| Yr 1 | $13,000 | +$963 | $13,963 |
| Yr 2 | $16,000 | +$2,255 | $18,255 |
| Yr 3 | $19,000 | +$3,904 | $22,904 |
| Yr 4 | $22,000 | +$5,938 | $27,938 |
| Yr 5 | $25,000 | +$8,390 | $33,390 |
| Yr 6 | $28,000 | +$11,295 | $39,295 |
| Yr 7 | $31,000 | +$14,689 | $45,689 |
| Yr 8 | $34,000 | +$18,615 | $52,615 |
| Yr 9 | $37,000 | +$23,115 | $60,115 |
| Yr 10 | $40,000 | +$28,238 | $68,238 |
| Yr 11 | $43,000 | +$34,035 | $77,035 |
| Yr 12 | $46,000 | +$40,562 | $86,562 |
| Yr 13 | $49,000 | +$47,880 | $96,880 |
| Yr 14 | $52,000 | +$56,054 | $108,054 |
| Yr 15 | $55,000 | +$65,156 | $120,156 |
Understanding the Power of Compound Interest
What is Compound Interest?
Compound interest is often described as "interest on interest." When you invest money, you earn interest on your initial principal. In the next compounding cycle, you earn interest on both your original principal **and** the accumulated interest from the previous cycle. Over time, this compounding loop creates an exponential curve that is the bedrock of long-term wealth building.
How do regular monthly deposits accelerate growth?
While a single initial deposit will compound over time, making recurring monthly contributions (an annuity) radically accelerates growth. Regular deposits continuously increase the base principal balance upon which compounding interest is calculated. This creates a powerful snowball effect that multiplies your long-term returns.
Why do compounding intervals matter?
The compounding frequency determines how many times interest is calculated and added back to your balance each year. For instance, **monthly compounding** divides the annual rate by 12 and applies it 12 times a year, whereas **annual compounding** applies the full rate once at the year's end. More frequent compounding means interest starts earning interest sooner, yielding higher final returns.
A Worked Example
Imagine starting with $10,000 and adding $500 every month for 30 years at a 7% annual return. You'd contribute $190,000 of your own money, but the balance grows to roughly $686,000 — meaning about $496,000 is pure compound growth.
The lesson is that time matters more than amount. The same $500 a month started just ten years later finishes with less than half as much, because the earliest dollars have the most years to compound. This is also why the projection shows nominal growth — to gauge real purchasing power, subtract an inflation assumption of 2–3% from your return.
Frequently Asked Questions
What is the Rule of 72?
The Rule of 72 estimates how long an investment takes to double: divide 72 by your annual return. At 8% a year, money roughly doubles every nine years — a quick way to gauge compounding without a full calculation.
What rate of return should I assume?
Historically the US stock market has averaged roughly 7% per year after inflation over the long run, but returns vary widely year to year. Using a conservative estimate avoids overstating your projected balance.
Does this account for inflation and taxes?
The projection shows nominal growth before taxes and inflation. To gauge real purchasing power, subtract an inflation assumption (often 2–3%) from your return, and remember tax-advantaged accounts like IRAs and 401(k)s shelter gains.
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