Investment Calculator
Project the future value of your investments with regular contributions.
Future Value with Regular Contributions
The first term is your starting balance compounding on its own. The second term is the future value of an annuity: every contribution compounds for the number of periods remaining after it is made — early contributions compound longest, which is why starting early matters more than contributing more later.
This calculator uses nominal compounding by default. If you enter an expected 7% return, remember that is a long-run average: real sequences fluctuate, and inflation subtracts roughly 2-3% per year from purchasing power.
Worked Example: $10,000 Initial + $300/Month at 7% for 20 Years
Monthly return: 7% ÷ 12 ≈ 0.5833% → r = 0.005833
Periods: 20 × 12 = 240
Initial growth: 10,000 × (1.005833)^240 ≈ $40,387
Contributions: 300 × [ (1.005833^240 − 1) ÷ 0.005833 ] ≈ $156,437
Total ≈ $196,824 — of which you contributed $82,000
Roughly $114,800 of the final balance is growth. Delaying the start by 5 years would cut the final value by nearly $70,000 — the strongest argument for starting now, even small.
Frequently Asked Questions
Is 7% a realistic return to assume?
The S&P 500 has averaged about 10% nominal, roughly 7% after inflation, over long periods. For planning, many advisors use 6-8% for diversified equity portfolios — conservative enough that a bad decade won't break the plan.
What is the difference between compound interest and compound returns?
Compound interest is fixed-rate (savings accounts, CDs). Compound returns apply to investments whose yearly result varies; the calculator's compounding math is identical, but actual investment paths will differ from the smooth average.
How do fees affect my final balance?
A 1% annual fee reduces a 7% gross return to 6% net. Over 30 years on $300/month, that gap alone is roughly $70,000 — fee share (expense ratio) is one of the few things you fully control.
Should I invest a lump sum or dollar-cost average?
Statistically, lump sum wins about two-thirds of the time because time in the market compounds. DCA reduces regret risk and timing risk; the calculator can model both by setting PMT = 0 or P = 0.
Authoritative Sources & Further Reading
Last reviewed: September 2026. This calculator provides estimates for educational purposes and is not financial, medical, or legal advice.
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Frequently Asked Questions
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