Interest Calculator
Free interest calculator for simple and compound interest. See total interest earned, final balance, growth over time, and year-by-year breakdown instantly with no signup.
Example Scenarios
Savings
$10k • 5% • 10 yr
CD
$25k • 4.5% • 5 yr
Monthly Deposits
$5k + $200/mo
Long Term
$10k • 7% • 20 yr
Interest Details View Results
Growth Analysis
Growth Over Time
Compounding Frequency Comparison
| Frequency | Final Balance | Interest |
|---|
Year-by-Year Growth
| Year | Start | Contributions | Interest | End |
|---|
How This Is Calculated
Compound interest uses A = P(1 + r/n)nt, with your own numbers plugged in:
Everything behind the Interest Calculator
Formulas, reference charts, and detailed answers — expand any section you need.
Daily vs. Monthly vs. Annual Compounding: Does Frequency Matter?
More frequent compounding earns slightly more at the same stated rate, but the effect is smaller than most people expect. The frequency comparison table shows all four frequencies with your exact inputs so the real difference is visible.
| Compounding | $10,000 at 5% for 10 Years |
|---|---|
| Annually | $16,289 |
| Quarterly | $16,436 |
| Monthly | $16,470 |
| Daily | $16,487 |
Interest Calculator: How Much Will My Money Earn?
This interest calculator computes both simple and compound interest and shows exactly how a balance grows over time. Enter a starting amount, annual rate, and time period, and the calculator displays total interest earned, final balance, and a year-by-year breakdown instantly. Toggle between simple and compound modes on the same inputs to see how much difference compounding makes with your own numbers.
Example: $10,000 at 5% for 10 years earns $5,000 in simple interest, but $6,470 with monthly compound interest.
Compound Interest Calculator: The Formula Explained
Compound interest pays interest on both the principal and previously earned interest, using the formula A = P(1 + r/n)^(nt), where P is principal, r is the annual rate, n is compounding periods per year, and t is time in years. The compound interest calculator applies this automatically and shows the result at every compounding frequency, since more frequent compounding produces a slightly higher final balance at the same stated rate.
Simple Interest Calculator: When Interest Doesn't Compound
Simple interest is calculated on the principal alone using I = Prt (principal times rate times time), with no interest earned on prior interest. It's common in auto loans, short-term personal loans, and some bonds. The simple interest calculator mode shows total interest and final amount, and the side-by-side toggle makes the gap against compound growth immediately visible on identical inputs.
Compound Interest Calculator With Monthly Contributions
Regular deposits change the math significantly, since each contribution starts its own compounding clock. Deposits mode combines your starting principal with monthly contributions and shows how much of the final balance came from deposits versus interest. This is the realistic scenario for most savers, and the one basic interest calculators skip.
Example: $5,000 starting principal plus $200 monthly at 6% for 15 years grows to about $70,300, of which roughly $29,300 is interest.
How Long to Reach a Savings Goal?
Target mode works in reverse: enter the amount you want to reach and either your monthly deposit or your deadline, and the calculator solves for the missing piece. It answers "how long until I have $50,000" or "how much do I need to save monthly to hit $100,000 by 2040" directly, without trial and error.