Compound Interest Calculator (2026) - Daily, Monthly & Annual

Reviewed by Financial Editor • Last updated: July 2026

See It In Action

Let's say you deposit $10,000 into an account earning a 5% annual return, compounded daily, and you don't add anything else.

After 1 year: $10,512.67 ($512.67 in interest)
After 10 years: $16,486.65 ($6,486.65 in interest)
After 20 years: $27,180.96 ($17,180.96 in interest — more than your original deposit)

Notice how the growth accelerates. In year one, you earn about $513. By year 20, you're earning over $1,300 in that single year alone — because you're now earning interest on nearly $27,000, not just your original $10,000. That's compounding at work.

Now add a monthly contribution of $200 to the same scenario, and after 20 years you'd have $109,387.69 — proof that consistent contributions matter as much as the rate itself.

Understand Compounding Frequency

When comparing different financial products, the compounding frequency can make a surprisingly large difference. A 5% rate compounded daily will yield a higher return than a 5.1% rate compounded annually. Use this calculator to compare different frequencies.

Compound Interest vs. Simple Interest

Simple interest is calculated only on your original principal — it never changes. Compound interest is calculated on your principal plus any interest you've already earned, so the interest itself starts earning interest.

	$10,000 at 5% for 10 years
Simple interest	$15,000.00
Compound interest (annual)	$16,288.95
Compound interest (daily)	$16,486.65

The difference may look small in year one, but it widens every year — this is why almost all savings accounts, CDs, and investment accounts use compound interest, not simple interest.

What Is APY, and How Does It Relate to Compounding?

Banks usually advertise a savings account's return as APY (Annual Percentage Yield), not a raw interest rate. APY already factors in the compounding frequency, so a 4.90% APY account compounded daily and a 5.00% APY account compounded monthly could earn you almost the same amount — the APY does the comparison work for you.

If you only have an interest rate (not APY) and want to know the compounding effect, that's exactly what this calculator solves — enter the rate and frequency separately to see the real dollar difference.

Exponential Growth Visualized

In the first few years, compound interest looks like a straight line. But over decades, the curve goes exponential as your interest starts earning its own interest. Use our tool to calculate your future wealth.

The Rule of 72

Want a fast way to estimate how long it takes your money to double, without opening a calculator? Divide 72 by your annual interest rate.

At 6% annual return → 72 ÷ 6 = 12 years to double
At 8% annual return → 72 ÷ 8 = 9 years to double
At 4% annual return → 72 ÷ 4 = 18 years to double

It's an approximation, not exact — use the calculator above for a precise figure — but it's a useful gut check when comparing offers.

Frequently Asked Questions

Compound interest is interest calculated on both your original principal and any interest that's already accumulated. It's often summarized as "interest on interest," and it's the main reason long-term savings and investments grow faster the longer you leave them untouched.

Compounding frequency is how often interest is calculated and added to your balance — daily, monthly, quarterly, or annually. More frequent compounding means slightly higher returns, because each round of interest starts earning its own interest sooner. The difference between daily and annual compounding is usually small (a few dollars per $10,000 per year) but grows over long timeframes.

A = P(1 + r/n)^(nt) • A = the final amount • P = principal (starting balance) • r = annual interest rate (as a decimal, so 5% = 0.05) • n = number of times interest compounds per year • t = number of years

Simple interest only applies to your original balance, so it grows in a straight line. Compound interest applies to your balance plus all interest earned so far, so it grows exponentially — slowly at first, then much faster in later years.

Not usually. A higher rate almost always beats more frequent compounding. For example, 5% compounded annually will outperform 4.9% compounded daily. Compounding frequency matters most when you're comparing two accounts with very similar rates.

It depends on the rate and compounding frequency. At a 5% annual return compounded daily, $10,000 grows to about $16,486.65 in 10 years — $6,486.65 in interest, with no additional contributions. Use the calculator above to test your own rate and timeframe.

Yes — often a bigger difference than the interest rate itself over long timeframes. Adding even $100–$200 a month can add tens of thousands of dollars to your final balance over 20–30 years, because each contribution gets its own runway to compound.

Yes, the underlying compound interest math is the same whether you're modeling a savings account, CD, or investment portfolio. Just note that investment returns (unlike a bank's stated APY) aren't guaranteed and typically fluctuate year to year — this calculator assumes a constant rate for simplicity.

This tool is for educational purposes only and does not constitute financial advice.
Check out our related calculators: Savings Calculator, Investment Calculator, ROI Calculator.