Daily Compound Interest Calculator

Use this daily compound interest calculator to see how a deposit grows when interest is added every day, and compare 365 and 360 day-count bases.

What it does

The Daily Compound Interest Calculator shows how a lump sum grows when interest is added every day rather than once a year. It applies a daily rate to the principal and lets the balance snowball over the number of days you choose.

Data sources & parameters

This calculator uses standard financial formulas and runs entirely in your browser. It needs no external rate data — your result is computed only from the values you enter above.

We always strive to use the latest data for every variable so our results and reports are as accurate as possible. Even so, errors are possible — you should not rely on this tool or its report alone, and we accept no liability for any decision made based on it.

The formula

FV = P × (1 + r/100/DC)^days, where r is the annual rate, DC the day-count basis and days the term

How it works

The annual rate is divided by the day-count basis (365 or 360) to get a daily rate, then the principal compounds day after day for the whole period. Each day's interest joins the balance and earns interest the next day.

Where it is used

Estimating daily-compounding savings or high-yield account growth
Comparing the 365-day and 360-day interest conventions
Seeing how a single deposit grows over weeks, months or years

Worked example

A deposit of $10,000.00 at 5% compounded daily over 365 days grows to …, earning … in interest.

What the daily compound interest calculator does

Enter a principal, an annual interest rate, the number of days and the day-count basis, 365 or 360, to match your account or loan. The calculator shows the balance at the end of the period and the interest earned, with a chart of the balance over time. Many high-yield savings accounts, money market accounts and some loans calculate interest daily even though they pay it monthly, so this shows what a deposit is doing between statements.

How daily compounding works

The annual rate is divided by the day-count basis to get a daily rate. Each day that rate is applied to the balance, the interest is added, and the next day the calculation runs on the slightly larger balance. The effect on any one day is tiny, but repeated every day of the year it produces more than simple interest, which is calculated only on the original principal.

The 365 versus 360 day-count basis

The 360-day convention is an old banking practice from before computers, when a year of twelve 30-day months made manual calculation easier. Dividing the annual rate by 360 gives a slightly larger daily rate, and applied across a full 365 days it credits a little more interest than the 365 basis. The difference is small but real; to check a bank's figures, use the convention that institution uses.

How much frequency matters

At 4%, the gap between daily and monthly compounding is less than one cent per 100 saved over a year. Moving from annual to monthly compounding captures most of the benefit; daily adds only a little more. Frequency matters more when the rate is high, since there is more interest each period to reinvest, and over long terms, when small daily gains build up. For a modest deposit at an ordinary rate over one year, the rate and the amount you save matter far more.

On a short horizon the chart looks almost straight; extend the number of days and it curves upward as interest builds on interest. Days can cover several years: 730 for two years, 1825 for five.

Reading the results

The result is nominal: it does not subtract tax on the interest or adjust for inflation. To see real purchasing power, subtract your expected inflation rate from the annual rate before entering it, and treat the interest as a pre-tax figure. Use the calculator to compare: raise the rate, lengthen the term or switch the day-count basis and see how the balance responds. It is also useful for checking a bank's interest figures and comparing accounts on the same basis.

This article is general information only and is not financial advice.

About This Daily Compound Interest Calculator

Use this daily compound interest calculator to get an instant estimate based on the figures you enter. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.

Frequently asked questions

How does daily compound interest work?

The annual rate is divided by the day-count basis, either 365 or 360, to produce a daily rate. That rate is applied to the balance every day, and each day's interest is added so the next day earns interest on a slightly larger amount. Over the full term this daily reinvestment produces more growth than compounding once a year at the same nominal rate.

What is the difference between a 365 and 360 day-count basis?

Both spread the same annual rate across the year, but a 360-day basis divides it into fewer, larger daily slices. Applied over a full 365 days, the 360 basis therefore credits slightly more interest. Banks and lenders choose one convention or the other, so match the setting to the product you are comparing.

Is daily compounding much better than monthly or annual?

It is better, but the gap is smaller than many expect. At 4%, daily compounding earns less than one cent more per 100 saved over a year than monthly compounding. The compounding frequency matters more at higher rates and over longer periods.

Does the calculator include tax or inflation?

No. It shows nominal growth before any tax on interest and before inflation. To gauge real purchasing power, subtract your expected inflation rate from the annual rate, and remember that interest may be taxable depending on where you live and the type of account.

Can I use it for more than one year?

Yes. Enter any number of days, including several years' worth. The formula compounds the principal across every day you specify, so 730 days models two years and 1825 days models five.

Is my data kept private?

Yes. The calculation runs entirely in your browser. Nothing you type is uploaded, stored, or shared with anyone.

About the author

Written and reviewed by

Taha Kheirandish

Economics student and independent researcher

Taha Kheirandish reads tax codes the way other people read maps — to find out where a system actually leads, not where it claims to go.

He is an economics student, and his work here is comparative by design. A pension deferral bonus in Quebec, a commuting allowance in Germany, a rent-increase ceiling in the Netherlands: each is a decision a government made about how money should move, and each reads differently once you set it beside eight others. He builds and checks these calculators across nine markets from primary sources — the regulation rather than a summary of it, the ministry’s own circular rather than a news item quoting it.

That is the editorial standard of the site as well as his habit. Every rate, threshold and bracket here carries the document it was read from and the date it takes effect, and gets re-checked when the law moves rather than when someone happens to notice.

He is a researcher, not a licensed adviser, and nothing on this site is personal financial advice. It is arithmetic done carefully with its sources shown — so that you can check it, and take it to someone who is.

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