Toolivaro

Free Compound Interest Calculator

Project how an investment grows with compound interest — with optional monthly contributions and yearly, quarterly, monthly, or daily compounding.

The compound interest calculator projects the future value of savings or investments using the standard formula, and it makes the power of compounding visible: a one-time 10,000 deposit at 5% annual interest grows to about 27,126 in 20 years with monthly compounding — nearly 17,000 of it pure interest. Enter an initial balance, an annual interest rate in percent, and a time period, and the tool returns the final value, the total interest earned, and the total amount you contributed. Add a monthly contribution and the tool includes it in the projection, converting the monthly amount into the compounding period you choose (yearly, quarterly, monthly, or daily) so the math stays consistent. Decimal arithmetic keeps the projection exact, the zero-rate case (pure contributions, no interest) is handled correctly, and the interest rate is never assumed to be a decimal — enter 5 for five percent. Everything is computed locally in your browser; no financial data leaves your device.

Processed locally in your browser

The money you start with.

Nominal rate per year, in percent.

How long the money grows.

Optional — extra amount added each month.

How is the result calculated?

10,000 at 5% for 20 years, monthly compounding

With principal 10000, rate 5, and 20 years, the final value is about 27,126 — the interest portion alone is about 17,126, more than the original deposit.

Input Value
principal 10000
annualRate 5
years 20
compounding monthly
Result ≈ 27,126 · 17,126 of it interest

Saving 200 a month for 10 years at 6%

With no initial balance, a 200 monthly contribution, and monthly compounding, the projection reaches about 32,829 — of which 24,000 came from the contributions themselves and about 8,829 from compounding.

Input Value
principal 0
annualRate 6
years 10
monthlyContribution 200
compounding monthly
Result ≈ 32,829 final value

What is the formula and its assumptions?

Future value with contributions

FV = P(1 + i)ⁿ + c × ((1 + i)ⁿ − 1) / i

Symbol Meaning
P initial balance (principal)
i rate per period = annual rate / (100 × periods per year)
n number of compounding periods = years × periods per year
c contribution per period = monthly × 12 / periods per year

No-interest case

FV = P + c × n

Symbol Meaning
P initial balance
c × n total contributions over the term

What are the most common mistakes?

  • Entering the rate as a decimal — 5 is five percent, not 0.05; using 0.05 produces a 100× smaller projection.
  • Forgetting to account for contributions as deposits: "interest on interest" applies to the whole balance, including money deposited years ago.
  • Treating the nominal rate as the effective rate — with daily compounding the effective annual rate is slightly higher.

What are the assumptions and limitations?

  • The projection assumes a constant rate of return for the entire term; real returns vary, and past performance does not predict the future.
  • Contributions are modeled as uniform deposits per compounding period rather than exact calendar dates.
  • The tool is educational — it is not investment advice, and it does not model taxes, inflation, or fees.

Where do the numbers come from?

Last reviewed August 11, 2026 · Version 1.0.0 · Toolivaro does not guarantee external content.

Business Loan Amortization Calculator Compute the monthly payment for any loan and see the full amortization schedule — or enter a payment to find how much you can borrow. Business Break-Even Calculator Find how many units you must sell — and at what revenue — to cover your fixed costs, from price and variable cost. Business Gross Profit Calculator Calculate gross profit and gross margin from revenue and cost of goods sold, with a target-revenue mode. Business Cash Runway Calculator Estimate how many months your business can operate before running out of cash, from balance, expenses, and income. Business Discount Calculator Calculate the final price after any percentage discount, the exact amount saved, and the discount between two prices.

Frequently asked questions

Why does compounding more frequently increase the result?

Interest earned earlier starts earning interest sooner. The same nominal annual rate compounded daily pays slightly more than the same rate compounded yearly because each day's interest joins the balance. The difference is small for a few years but compounds into a meaningful gap over decades.

How is a monthly contribution handled with daily compounding?

The monthly amount is converted to a per-period amount (monthly × 12 ÷ periods per year) and assumed to be deposited uniformly across the period. This is a documented modeling assumption — real deposits land on specific dates, which changes the result by a small amount.

What does the total interest figure mean?

Total interest is the final value minus everything you put in (initial balance plus all contributions). It is the portion of the outcome produced by compounding rather than by your own savings.

Part of Startup and freelance finance calculators

Found a mistake or have a correction? Report it — we review every correction.

Was this helpful?

Reviewed by the Toolivaro editorial team per our methodology Methodology · Editorial policy