Kaip apskaičiuoti Compound Interest
Kas yra Compound Interest?
Compound interest earns returns on both principal and previously earned interest. The frequency of compounding (annual, monthly, daily) affects the effective annual rate (EAR), with more frequent compounding yielding slightly higher returns.
Formulė
A = P(1+r/n)^(nt) + PMT×[(1+r/n)^(nt)−1]/(r/n) where PMT=regular payment
- A
- Final Amount ($)
- P
- Principal ($)
- r
- Annual Rate (%)
Žingsnis po žingsnio vadovas
- 1A = P × (1 + r/n)^(n×t)
- 2P = principal, r = annual rate, n = compounding periods/year, t = years
- 3With monthly contributions (PMT): add PMT × ((1+r/n)^(n×t) − 1) ÷ (r/n)
- 4EAR = (1 + r/n)^n − 1
Worked Examples
Įvestis
$10,000 at 7% for 20 years, monthly compounding
Rezultatas
$40,642 — vs $38,697 with annual compounding
Įvestis
Same with $200/month added
Rezultatas
$127,000 — contributions quadruple the outcome
Frequently Asked Questions
How is compound interest different from simple interest?
Simple interest: I = PRT (linear growth). Compound interest: A = P(1+r)^t (exponential growth). Compound interest accelerates as interest earns interest.
How often should interest compound?
More frequent compounding = higher returns. Annual vs daily compounding can differ by 0.5–1% annually. Continuous compounding (e) is the theoretical maximum.
What is the "Rule of 72"?
Years to double ≈ 72 / interest rate. At 8%, money doubles in ≈9 years. Quick mental estimation for long-term growth.
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