ConverterHub

Compound Interest Calculator

See the power of compounding from principal, annual rate and term.

How it is calculated

The balance after compounding is A = P × (1 + r/n)n×t, where P is the starting principal, r the annual rate as a decimal (the tool divides your percentage by 100), n the number of compounding periods per year and t the term in years. Interest earned is A − P. The principal, term and frequency must be greater than zero and the rate cannot be negative, otherwise no result is shown. The tool models a single lump sum with no further deposits, no tax and no fees, and results are shown in dollars rounded to cents.

Worked example

Take a principal of $10,000.00 at 6% a year, compounded monthly (n = 12) for 10 years. The periodic rate is 0.06 / 12 = 0.005, and there are 12 × 10 = 120 periods. The growth factor is 1.005120 ≈ 1.8194. Multiplying: A = 10,000 × 1.8194, which gives a final amount of $18,193.97. Interest earned is 18,193.97 − 10,000 = $8,193.97.

Try this example →

Common mistakes

  • Entering the rate as a decimal (0.06) instead of a percentage (6); the tool expects the percentage.
  • Entering the term in months while the field is in years, which hugely understates growth.
  • Using the nominal annual rate of an account that quotes an effective yield (APY); the two are not the same number.
  • Expecting the result to include regular monthly deposits; this tool grows one lump sum only.
  • Forgetting that inflation and tax reduce the real value of the final amount.

About this calculator

Compound interest describes what happens when the interest an amount earns is added back to the balance, so future interest is calculated on a growing base rather than just the original sum. This calculator projects that snowball effect forward using the principal, the rate, how often interest is compounded, and the length of time, showing how the growth curve steepens the longer the money stays invested.

It is used by savers comparing deposit accounts, investors estimating how a lump sum or regular contributions might grow, and students learning why starting early matters more than the rate itself in many cases. It also helps illustrate the flip side, since the same math applies to debt that accrues interest on unpaid interest.

Was this helpful?

You can pick up to 3 reactions.

Comments (0)

  • Be the first to comment.

Popular calculators

Loan Calculator

Monthly payment, total interest and full amortization schedule.

Percentage Calculator

Percent change, percent of, and ratio calculations.

Discount Calculator

Calculate final price, savings, and discount amount.

BMI Calculator

Body mass index from height and weight (metric or imperial).

Age Calculator

Compute your exact age in years, months and days from a birth date.

Turkish VAT (KDV) Calculator

Add or extract Turkish VAT (KDV) at 1%, 10% or 20%.

All Calculators