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Work backward from a goal to the monthly amount that could get you there.
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Compound interest calculator
Let your money grow a little mane.
Your numbers
See how a starting amount, regular deposits, and time could grow your money.
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THE MATH, WITHOUT THE MYSTERY
What’s actually happening here?
Compound interest means your growth can earn growth of its own. The longer the runway, the more noticeable that effect can become. Negative returns work in the opposite direction.
P is your starting amount, M is your monthly deposit, and n is the number of months. We convert the nominal annual rate r, compounded m times per year, into an equivalent monthly rate: i = (1 + r/m)^(m/12) − 1. For start-of-month deposits, the deposit term is multiplied by (1 + i).
THE FORMULA
FV = P(1 + i)ⁿ + M × ((1 + i)ⁿ − 1) / i
A small example
Start with 1,000, add nothing, and earn 5% compounded yearly. After 2 years: 1,000 × 1.05² = 1,102.50. The second year earns 52.50, not just 50.
Further reading
SEC Investor.gov · Compound interest calculatorGOOD QUESTIONS
A few things worth knowing.
Is this a prediction?
No. It is a constant-rate scenario. Real investments can lose money, and market returns do not arrive at a smooth, fixed rate.
What changes when I deposit at the start?
Each deposit gets one extra month of modeled growth. That helps at a positive rate and hurts at a negative rate.
Does changing the currency convert my money?
No. The currency setting changes the label and formatting only. Use the same currency for every input.