Estate Tax Calculator
Estimate potential estate-tax exposure using gross estate value, deductions, lifetime taxable gifts, the remaining exemption, and an optional flat state estate-tax rate.
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Compound Interest Calculator
Calculate compound interest growth with any compounding frequency — daily, monthly, quarterly, or annually. Add regular contributions, see a year-by-year growth schedule, effective annual rate (EAR), Rule of 72, and a visual balance chart.
Investment Details
$
%
years
$
Final Balance
$20,096.60
after 10 years at 7% (monthly)
Principal49.8%
Interest50.2%
Breakdown
Initial Principal$10,000.00
Interest Earned$10,096.61
Total Invested$10,000.00
Final Balance$20,096.60
Effective Annual Rate
7.229%
Rule of 72
10.29 yrs
to double
Balance Growth by Year
1y
5y
10y
Principal + ContributionsInterest
Step-by-Step Calculation
Formula: A = P(1 + r/n)^(nt)
P = 10000 (principal)
r = 7% / 100 = 0.07
n = 12 (compounding periods/year)
t = 10 years
(1 + r/n)^(nt) = 2.0097
A = 10000 × 2.0097 = 20,096.60Frequency Comparison — Same Principal & Rate
| Frequency | Final Balance | Interest Earned |
|---|---|---|
| Annually | $19,671.51 | $9,671.51 |
| Semi-annually | $19,897.89 | $9,897.89 |
| Quarterly | $20,015.97 | $10,015.97 |
| Monthly(selected) | $20,096.61 | $10,096.61 |
| Weekly | $20,128.05 | $10,128.05 |
| Daily | $20,136.18 | $10,136.18 |
What Is Compound Interest?
Compound interest is interest calculated on both your initial principal and the accumulated interest from all previous periods. This means your money grows not just from the original deposit, but from an ever-increasing balance — creating exponential growth over time. Einstein famously called it the "eighth wonder of the world."
The key difference from simple interest: with simple interest, you earn the same dollar amount every year (a fixed percentage of the original principal). With compound interest, each year's interest is added to the balance, so the next year you earn interest on a larger amount — and this compounds over and over.
The power of time: $10,000 at 7% for 30 years with monthly compounding grows to $81,645 — over 8× your original investment, with $71,645 in pure interest. After just 10 years it's $20,097 — most of the growth happens in the final years due to compounding.
How Compound Interest Is Calculated
The standard compound interest formula:
A = P(1 + r/n)^(nt)
Where:
A = final amount
P = principal (initial deposit)
r = annual interest rate (as decimal, e.g. 0.07 for 7%)
n = number of compounding periods per year
t = time in yearsExample — No Contributions
P = $10,000r = 7% → 0.07n = 12 (monthly)t = 10 years(1 + 0.07/12)^(12×10) = 2.0097A = $10,000 × 2.0097 = $20,097Example — With Monthly Contributions
P = $10,000PMT = $200/monthr = 7%, n = 12, t = 10 yrsBase: $20,097Contrib. part: ~$34,616Total: ~$34,719Compound Interest vs Simple Interest
The difference becomes dramatic over time. Simple interest grows linearly; compound interest grows exponentially. Here's a direct comparison for $10,000 at 7%:
| Year | Simple (7%) | Compound Monthly | Extra from Compounding |
|---|---|---|---|
| 1 | $10,700 | $10,723 | +$23 |
| 5 | $13,500 | $14,176 | +$676 |
| 10 | $17,000 | $20,097 | +$3,097 |
| 20 | $24,000 | $40,388 | +$16,388 |
| 30 | $31,000 | $81,165 | +$50,165 |
Based on $10,000 principal at 7% annual rate, monthly compounding.
5 Ways to Maximize Compound Interest
⏰
Start as early as possible
Time is the most powerful variable. Starting at 25 vs 35 with the same contributions can mean 2–3× more wealth at retirement, purely due to extra compounding years.
🔁
Reinvest all returns
Never withdraw interest or dividends. Reinvesting each payout immediately lets every dollar start compounding, maximizing the snowball effect.
📅
Choose higher compounding frequency
Daily or monthly compounding beats annual compounding for the same nominal rate. When comparing savings accounts, always compare Effective Annual Rates (EAR).
💰
Add regular contributions
Even small monthly contributions make an enormous difference over decades. $100/month at 7% for 30 years adds $121,997 to your balance beyond the principal alone.
📉
Minimize fees and taxes
A 1% annual management fee can reduce your final balance by 20–25% over 30 years. Tax-advantaged accounts (401k, IRA, ISA) let compounding work on pre-tax money.
🎯
Use the Rule of 72
Divide 72 by your interest rate to estimate doubling time. 6% → 12 years. 9% → 8 years. 12% → 6 years. Use this to quickly compare investment options.
Frequently Asked Questions
Explore This Tool in Context
Compound Interest Calculator is part of the Financial Calculators collection. If you want a broader view of similar workflows, open the Financial Calculators category page or browse all QuickTools categories.
Common next steps after this tool include Estate Tax Calculator, Social Security Calculator and Annuity Payout Calculator.
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