Online Compound Interest Calculator
Compound Interest Calculator solves for the future total, principal, interest, rate, or time, with compounding from annually all the way to continuously.
Find
29,524.91
23,370.10
3,524.96
1.825
7.3
What Is This Tool?
The Compound Interest Calculator finds any one part of a compound-interest problem. Choose what to solve for — the future total (A), the principal needed for a target (P), the principal behind a given interest amount, the rate (R), or the time (T) — then enter the values you know. You can set how often interest compounds, from annually up to daily or continuously. Unlike simple interest, each period's interest is added to the balance and earns further interest. The result can be downloaded as a PDF.
How to Use This Tool?
- Choose what you want to solve for.
- Enter the values you already know.
- Pick how often interest compounds.
- Click Calculate to find the missing value.
Key Features
- Solves for the total, principal, rate, or time.
- Compounds from annually through to continuously.
- Adds each period's interest to the balance so it earns more interest.
- Supports 365-day and 360-day daily compounding.
- Shows a single clear result with a PDF download.
Examples
- $23,000 at 2.5% for 10 years, compounded monthly, grows to $29,524.91.
- To reach $30,000 in 10 years at 2.5%, you'd start with $23,370.10.
- Earning $1,000 of interest at 2.5% over 10 years needs $3,524.96 of principal.
- Growing $25,000 to $30,000 in 10 years implies a 1.825% rate.
Common Use Cases
- Projecting the future value of a savings account.
- Finding the deposit needed to reach a target amount.
- Solving for the rate that turns one balance into another.
- Estimating how long an investment takes to grow.
- Comparing compounding frequencies side by side.
Tips & Best Practices
- Match the compounding frequency to your account's terms.
- Remember more frequent compounding yields slightly more interest.
- Use continuously compounding as the theoretical upper bound.
- Keep the total greater than the principal when solving for rate or time.
- Use a simple interest calculator when interest isn't reinvested.
Limitations
- It assumes a constant rate and a single lump-sum principal.
- Regular contributions or withdrawals are not modeled.
- Taxes, fees, and inflation are not accounted for.
- Nothing is saved between sessions — only the current result can be exported as a PDF.
Frequently Asked Questions
- What is compound interest?
- Interest calculated on both the original principal and the interest already earned, so the balance grows faster over time.
- How does compounding frequency affect the result?
- More frequent compounding adds interest sooner, producing a slightly higher total for the same nominal rate.
- What does compounding 'continuously' mean?
- It's the theoretical limit of compounding at every instant, giving the highest total for a given rate.
- How is this different from simple interest?
- Simple interest is calculated only on the original principal, while compound interest also earns interest on accumulated interest.
Key Terminology
- Compound interest
- Interest earned on both the principal and previously accumulated interest.
- Principal
- The original amount invested or borrowed.
- Compounding frequency
- How often interest is added to the balance, such as monthly or daily.
- Continuous compounding
- Compounding at every instant, the theoretical maximum frequency.
- Rate
- The annual percentage at which interest accrues.