Compound Interest Calculator Online
Project how a balance grows with compound interest and optional regular contributions, right in your browser. Estimates only, not financial advice.
The Compound Interest Calculator runs entirely in your browser. The principal, rate, term, and contribution figures you enter never leave your device and are not uploaded to ArrayKit. Results are estimates only, not financial advice.
Open the Savings Calculator
About Compound Interest Calculator
Compound Interest Calculator projects how a starting balance grows over time when interest is added back to the principal and earns interest itself. Enter a principal, annual rate, term in years, and compounding frequency — annually, semi-annually, quarterly, monthly, or daily — and it applies A = P(1 + r/n)^(n·t) to compute the final balance. Add an optional regular contribution to see how consistent monthly or quarterly deposits accelerate growth, and review a year-by-year balance table alongside the total interest earned. It is useful for comparing savings accounts, CDs, or retirement contribution scenarios before committing real money. These are estimates only, not financial advice — verify with a qualified professional. Everything runs locally in your browser; your numbers are never uploaded.
Features
- Computes final balance using the standard compound interest formula A = P(1 + r/n)^(n·t)
- Choose compounding frequency: annually, semi-annually, quarterly, monthly, or daily
- Add an optional recurring contribution with its own frequency
- Shows total contributions and total interest earned separately from the final balance
- Year-by-year balance table so you can see growth accelerate over time
- Copy a plain-text summary of the full result in one click
- Clear error messages for an invalid principal, rate, or term
- Runs entirely on your device — figures are never sent anywhere
How to use the Compound Interest Calculator
- Enter a starting principal, annual interest rate, and number of years
- Pick a compounding frequency such as monthly or daily
- Optionally add a regular contribution amount and its frequency
- Read the final balance, total contributions, and total interest
- Scroll the year-by-year table to see how the balance compounds
Example
Input
$1,000, 5%, 10 yr, monthly
Output
Final balance: $1,647.01
Interest: $647.01
Common errors & troubleshooting
- Interest rate typed as a decimal (0.05) instead of a percentage. — Enter the annual rate as a whole percentage, such as 5, not 0.05 — the calculator already divides by 100 internally.
- Final balance looks too low compared to an online estimate. — Check that the compounding frequency matches the account you are modeling — daily and monthly compounding produce noticeably higher balances than annual compounding at the same rate.
- Total contributions field shows $0 even though an amount was entered. — Make sure a contribution frequency is selected — the amount alone is not applied until a frequency (monthly, quarterly, or annually) is chosen.
- Year-by-year table only shows recent years for a long term. — The table shows the last 12 years to stay readable; the final balance and total interest figures above it always reflect the full term.
Frequently asked questions
- What formula does the Compound Interest Calculator use?
- It uses the standard compound interest formula A = P(1 + r/n)^(n·t), where P is the principal, r is the annual rate, n is the compounding frequency per year, and t is the term in years. Regular contributions are projected separately as a future value of a series and added to that result.
- How does the Compound Interest Calculator handle regular contributions?
- Enter an amount and a contribution frequency (monthly, quarterly, or annually) alongside the principal. The calculator adds the future value of those recurring deposits to the compounded principal so you can see how ongoing saving changes the final balance.
- Why does compounding frequency change the result so much?
- More frequent compounding means interest is added to the balance more often, so each addition starts earning interest sooner. Daily compounding at a given rate produces a higher final balance than annual compounding at the same rate.
- Is the Compound Interest Calculator's output financial advice?
- No. It produces mathematical estimates based on the numbers you enter. Actual account terms, fees, taxes, and rate changes can affect real results, so verify important decisions with a qualified financial professional.
- Does the Compound Interest Calculator upload my savings numbers?
- No. All calculations run locally in your browser. The principal, rate, and contribution figures you enter stay on your device and are never uploaded to ArrayKit.
- Can I model daily compound interest with this calculator?
- Yes. Select the Daily option in the compounding frequency control and the calculator applies n = 365 in the formula, giving you a close approximation of daily compounding growth.
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