$1,000 plus $100.00/mo at 6%
- Total contributions
- $13,000.00
- Estimated interest
- $5,207.33
- Effective annual rate
- 6.1677811865%
Compound Interest Calculator
Use this free compound interest calculator to estimate future value, total contributions, and interest from principal, deposits, rate, time, and compounding frequency.
Estimate, not advicePayment or total shownExample inputsTab-only history
Formula steps
- Compound 12 times per year.
- Convert compounding to an effective annual rate.
- Convert effective annual growth to monthly growth for contributions.
- Ending balance includes starting amount, monthly contributions, and estimated interest.
Examples
Recent answers
Recent compound interest estimates will appear here.
Compound interest estimates do not include taxes, fees, account limits, risk, or guaranteed returns.
Inputs and recent answers stay in this browser tab and are not sent to a server.
How to use the Compound Interest Calculator
- Enter the requested dollar amounts, rates, terms, tax settings, or contribution details.
- Use rates as percentages, such as 6.5 for 6.5%, and check whether a field asks for a monthly or annual amount.
- Press the calculate button to see the answer, supporting metrics, and formula steps.
- Use the result as a planning estimate only, then copy it if the assumptions look right.
What people use it for
Estimate how compound interest can grow savings over time.
Compare monthly deposits with a starting amount.
Test annual, quarterly, monthly, or daily compounding assumptions.
Separate contributions from estimated interest earned.
Quick examples
Savings growth
$1,000, $100/month, 6%, 10 yearsAbout $18,207.33 ending balance, with $13,000 contributed and about $5,207.33 interest
Daily compounding
$5,000 at 4.5% for 10 years, dailyAbout $7,841.34 ending balance and about 4.60% effective annual rate
No deposits
$10,000 at 5% for 20 years, monthlyAbout $27,126.40 ending balance and about $17,126.40 interest
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Compound Interest CalculatorSee slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- FinanceBrowse related calculators and utilities in the same category.
- Calculator and utility guidesFind more guides that use real tool inputs and example numbers.
- All free toolsSearch every live tool, converter, calculator, AI helper, and browser utility.
Frequently asked questions
Plain-language answers about when to use the estimate, what your numbers mean, what is left out, and how privacy works.
When should I use the Compound Interest Calculator?
Use it when you want to test the exact inputs on this page: Estimate how compound interest can grow savings over time. Compare monthly deposits with a starting amount. The result is a check against your assumptions, not proof that a lender, tax app, broker, platform, or provider will use the same number.
What do the main Compound Interest Calculator inputs mean?
Initial amount means the starting balance before new deposits and compound growth. Monthly contribution means the amount added each month in this simple model. The calculator treats deposits as end-of-month additions. Annual rate means the stated yearly rate entered as a normal percent, such as 6 for 6%. Time means how many years the estimate runs. Use 0.5 for 6 months or 1.5 for 18 months. Compounding frequency means how often interest is added back to the balance before the monthly contribution timing is modeled.
How does compound interest work in this calculator?
Interest is added back to the balance, then the larger balance can earn more interest later. The calculator first converts your annual rate through the compounding frequency you choose, then applies monthly growth and monthly deposits.
Are monthly deposits added at the start or end of the month?
This model treats monthly deposits as end-of-month contributions. That is a clean planning assumption, but a real bank, brokerage, or savings app can use different timing.
What is effective annual rate?
Effective annual rate shows the modeled one-year effect after compounding. For example, a stated 6% annual rate compounded monthly becomes about 6.17% effective annual growth before taxes, fees, or account rules.
Is this the same as APY?
No. APY is the official account disclosure from a bank or credit union. This calculator estimates compounding from the numbers you enter, but the real APY, exact compounding, fees, balance tiers, and withdrawal rules come from the account agreement.
What is the Compound Interest Calculator doing with my numbers?
In plain language: The calculator converts the stated annual rate to an effective monthly growth rate from the selected compounding frequency, then compounds principal and monthly deposits. For the default example, $1,000 plus $100 each month at a stated 6% annual rate for 10 years projects about $18,207.33, with $13,000 contributed and about $5,207.33 estimated interest.
How should I read the Compound Interest Calculator answer?
Start with ending balance, then compare total contributions with estimated interest. Contributions are your money going in; estimated interest is the growth from the rate and compounding assumption.
What does this estimate leave out?
This is a simple growth estimate. It does not include APY disclosures, taxes, fees, withdrawals, minimum balances, changing rates, investment losses, account limits, inflation, or bank-specific compounding rules. For bank accounts, compare the official APY and account disclosure. For investing, compare fees, taxes, inflation, risk, and whether the return assumption is realistic.
What should I double-check before copying the result?
Check that the rate is annual, the time is in years, the frequency matches the account or scenario, and the percent is entered as 6 for 6%, not 0.06.
Does the site save my finance inputs?
No. The calculator runs in your browser tab. Recent answers stay only on the page while you use it, and they are not sent to a server.