Калькулятор сложных процентов

Обзор

Compound interest is interest earned on both your original principal and on previously-accumulated interest. Albert Einstein reputedly called it 'the most powerful force in the universe' — though that quote is apocryphal, the underlying math is real. A modest 7% annual return doubles your money every 10 years through compounding. Over 40 years of working life, a single $10,000 investment becomes about $150,000 without adding another dollar. Understanding this changes how you think about retirement savings, debt, and time itself.

Как пользоваться (по шагам)

1. 1

   Enter your starting amount and monthly contribution

   Even a modest monthly addition dwarfs lump-sum contributions over decades. Test a $0 initial + $200/month to feel the dragnet effect.

2. 2

   Set the annual rate and number of years

   Use a realistic rate — long-term stock market averages run ~7% before inflation, ~5% after. Bonds and savings accounts run much lower.

3. 3

   Compare scenarios side by side

   Try 'start 5 years earlier' vs 'invest more later' — the early-start version almost always wins. This is the most important number to see for retirement planning.

Как это работает

The formula is A = P(1 + r/n)^(nt), where A is the final amount, P is principal, r is annual interest rate, n is compounding periods per year, and t is years. With monthly compounding (n=12), a 5% annual rate effectively becomes ~5.116% (the 'APY' or annual percentage yield). The calculator handles all combinations — you input the principal, optional regular contributions, rate, time, and compounding frequency, and it shows both the final balance and a year-by-year breakdown.

Когда пригодится

Run this when planning retirement contributions to see how starting earlier dramatically changes outcomes. Compare loan offers by computing total interest paid (compound interest works against you on debt). Evaluate whether to invest in index funds vs paying off low-interest debt. Show kids and teens what saving $50/month from age 18 turns into by age 65 — the result is shocking enough to motivate lifetime saving habits.

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