Daily vs Monthly Compound Interest

Daily vs monthly vs annual compounding

The examples hold the nominal annual rate fixed. AER/APY is an effective annual rate that already includes compounding; accounts with the same AER do not earn different annual returns solely because of crediting frequency.

Compounding frequency controls how often interest is calculated and added to the balance. The more frequently interest is added, the more often new interest can start earning interest itself.

At the same nominal annual rate, daily compounding normally produces a little more than monthly compounding, and monthly compounding normally produces a little more than annual compounding.

Example: £10,000 at 5% for 10 years

This table compares the same starting amount and rate using different compounding frequencies.

Compare monthly compounding in the calculator or open daily compounding.

For a closer look at the fixed-365-day convention and how it differs from AER, use the daily compound interest calculator and guide.

Is continuous compounding the same as daily?

No. Daily compounding uses a finite number of interest periods: 365 per year in this model. Continuous compounding is the mathematical limit as the number of periods increases without bound. At the same positive nominal annual rate, continuous compounding produces slightly more than daily compounding.

Daily:      A = P × (1 + r/365)^(365 × t)
Continuous: A = P × e^(r × t)

Here P is the starting balance, r is the nominal annual rate as a decimal and t is the number of years. With £10,000 at 5% for ten years and no payments, the daily result is £16,486.65 and the continuous result is £16,487.21: a difference of approximately £0.56, not a dramatic extra return. The daily example uses a fixed 365-day convention rather than actual calendar-day counting.

This comparison holds the nominal annual rate fixed. If two models have the same effective annual rate (AER/APY), their equivalent one-year growth factor is the same. With no cash flows and the same effective rate throughout, they also give the same balance over this whole-year term. For a real account, check its quoted rate, day-count, payment timing, fees and interest-crediting terms rather than assuming that “continuous” or “daily” is automatically better.

Why the difference can be small

People often expect daily compounding to be dramatically better than monthly compounding. In reality, if the same nominal annual rate is used, the difference is usually much smaller than the difference caused by changing the rate, the time period or the regular contribution amount.

When compounding frequency matters most

• When comparing products with similar quoted rates.
• When modelling long time periods.
• When balances are large enough for small percentage differences to become meaningful.
• When comparing loans or debts where compounding can work against you.

Best default for estimates

If you do not know the exact compounding frequency, monthly compounding is often a useful default for savings and investment-style estimates. For product-specific calculations, use the frequency stated in the terms.