Compound Interest Calculator
See exactly how your savings grow, with regular contributions factored in correctly.
Also known as: Savings calculator, Investment growth calculator, Future value calculator
How it works
- 1Enter your starting amount, annual interest rate, and time period in years.
- 2Choose a compounding frequency — annually, semi-annually, quarterly, monthly, or daily.
- 3Optionally enter a regular contribution amount for each compounding period.
- 4Review the final balance, total interest earned, and year-by-year breakdown, or download it as a CSV.
Why use Compound Interest Calculator
Correctly handles contributions
Simulates period by period instead of approximating, so regular contributions line up exactly with your chosen compounding frequency.
5 compounding frequencies
Model annual, semi-annual, quarterly, monthly, or daily compounding — not just one fixed option.
Year-by-year breakdown
See contributions and interest earned separately for every year, not just a single final number.
CSV export
Download the full year-by-year schedule for use in a spreadsheet or financial plan.
Growth multiple shown
See your final balance expressed as a multiple of what you actually put in, making the effect of compounding immediately clear.
Nothing uploaded
Every projection is calculated entirely in your browser and never transmitted anywhere.
Who uses Compound Interest Calculator
Planning retirement savings
Project how a retirement account grows with regular monthly contributions over several decades.
Comparing savings accounts
See how different interest rates and compounding frequencies affect long-term growth for the same contribution plan.
Setting a savings goal
Work out roughly how much a monthly deposit needs to be to reach a target balance by a certain year.
Teaching compound interest
Show the year-by-year split between contributions and interest earned to illustrate how compounding actually works.
Modeling an investment projection
Estimate long-term growth of a lump sum plus regular investment contributions at an assumed average return.
Evaluating a CD or fixed deposit
Calculate the exact maturity value of a fixed-term deposit at a specific compounding frequency.
About Compound Interest Calculator
Compound interest is often explained with a single clean formula, but that formula only tells the full story for a lump sum with no further deposits. Most real saving and investing involves both a starting amount and regular ongoing contributions — a monthly deposit into a savings account, a retirement contribution, a recurring investment — and a lot of "compound interest calculators" either ignore contributions entirely or bolt on an approximation that doesn't quite match the selected compounding frequency.
This tool avoids that gap by simulating growth period by period rather than relying on a single closed-form formula: for each compounding period (annual, semi-annual, quarterly, monthly, or daily), it applies interest to the current balance, then adds the contribution for that period, exactly matching how a real bank or brokerage account would actually compound. The result lines up exactly with the standard annuity formula in every case, but stays accurate even as you change the compounding frequency.
The year-by-year breakdown shows contributions and interest earned separately for every year of the projection, which makes an easy-to-miss fact of compound growth visible: in the early years, most of the balance increase comes from your own contributions, but in later years, interest earned starts to outpace what you're actually putting in — the growth compounds, exactly as the name suggests.
Every projection runs directly in your browser using straightforward period-by-period arithmetic — there's no server involved, and no financial data about your savings goals ever leaves your device.
Compound Interest Calculator vs. other options
How Open Tools Library compares to desktop software and other online tools.
| Feature | Open Tools Library | Desktop software | Other online tools |
|---|---|---|---|
| Price | Free, unlimited | N/A | Usually free |
| Regular contributions | Correctly simulated per period | N/A | Often approximated or missing |
| Compounding frequency options | 5 choices | N/A | Often fixed to 1 |
| Year-by-year detail | Full breakdown, downloadable | N/A | Often final number only |
| Data privacy | Never leaves your device | N/A | Varies |
Pro tips
- More frequent compounding (daily vs. annually) produces a slightly higher final balance at the same stated annual rate — the difference grows with both the rate and the time period.
- The "additional deposit" field is per compounding period, not always per month — check the label, which updates to match your selected frequency.
- In the early years, most balance growth comes from contributions; in later years, interest earned typically overtakes it — the year-by-year table makes this crossover visible.
- A 0% contribution still works correctly — the calculator handles a pure lump-sum projection with no regular deposits.
- For a rough estimate of a savings goal, try a few different time periods to see how a small increase in years compounds into a much larger final balance.
Technical specs
- Compounding frequencies
- Annually, semi-annually, quarterly, monthly, daily
- Contribution timing
- End of each compounding period (ordinary annuity)
- Simulation method
- Period-by-period, not a single approximated formula
- Export
- Year-by-year schedule as CSV
- Processing location
- 100% local, in your browser
Privacy & security
A savings goal or investment amount is personal financial information, even in a simple projection — it deserves to stay on your own device.
Every projection is calculated locally in your browser — your financial details are never transmitted anywhere.
No account, no email, no login — just numbers in, a projection out.
The CSV you download is generated and saved directly by your browser, with no server involved.
Equally private whether you're projecting a small savings account or a long-term investment plan.
Frequently asked questions
Is my financial information sent anywhere?
No. Every projection is calculated entirely in your browser — nothing is ever transmitted.
What formula does this use?
Rather than a single closed-form formula, it simulates each compounding period directly: interest accrues on the current balance, then the period's contribution is added — repeated for every period in the time frame.
Does this account for taxes or inflation?
No — this is a pre-tax, nominal (not inflation-adjusted) growth projection. Real-world after-tax, inflation-adjusted returns will typically be lower.
Can I use this for investments, not just savings accounts?
Yes, as long as you're comfortable treating the entered rate as a fixed annual return — actual investment returns vary year to year, while this tool assumes a constant rate for projection purposes.
Why does interest earned grow faster in later years?
That's compound interest at work — interest is earned not just on your contributions but on all previously earned interest too, so the effect accelerates the longer the money stays invested.
Can I download the full breakdown?
Yes, the complete year-by-year schedule downloads as a CSV file for use in a spreadsheet.
Troubleshooting
Changing the compounding frequency changes my final balance a lot
This is expected and correct — more frequent compounding (like daily) grows a balance slightly faster than less frequent compounding (like annually) at the same stated rate, and the gap widens over long time periods.
My contribution amount doesn't match what I expected for the total
The contribution field is per compounding period, not necessarily per month — if you selected quarterly compounding, a contribution of $100 means $100 per quarter, not per month. The field label updates to reflect this.
Can I model contributions at a different frequency than compounding?
Not directly in this version — contributions are tied to the compounding period you select. Choose monthly compounding if you want to model monthly contributions specifically.
The year-by-year table has fewer rows than the number of years I entered
Each row represents one full year; a non-whole number of years (like 10.5) will show a final partial-year row for the remainder.
Related searches
Landed here looking for something worded a little differently? Compound Interest Calculator covers all of these too:
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