Actual/365 Interest: Why Your Bank Statement Doesn't Match ÷12 Math

Take a $300,000 loan at 6.5% a year over 30 years, paid out on January 15. Divide the annual rate by 12 and the interest for the period from February 15 to March 15 is $1,623.53. Charge the same rate on the actual 28 days instead, divided by 365, and that period's interest is $1,494.69, which is $128.84 less. The next period, March 15 to April 15, has 31 days and costs $30.57 more than the ÷12 figure.

The monthly payment is $1,896.20 either way. What changes is how that payment splits between interest and principal, and that split is exactly what you see on a bank statement. If your statement shows interest that goes up and down from month to month while your calculator shows a smooth decline, the two are probably counting days differently.

Neither method is a trick. They are two ways of turning an annual rate into a charge for one month. Loan Calculator can do both, so your schedule can follow the same rule as your statement.

What should you compare?

When your own numbers and the lender's numbers don't match, check these before assuming anyone made a mistake:

• How the contract counts days: whether interest is described as the annual rate divided by 12, or charged per day over a 365-day year.
• The disbursement date: with actual days, the date the money was paid out decides how long each period is.
• Interest per period: under actual days it moves with the calendar, higher in 31-day months and lower in February.
• The last payment: if the regular payment stays fixed, any difference builds up and shows in the final payment.
• Total interest over the life of the loan: usually close under both methods, but not identical.

Day-count methods at a glance

Figures are for $300,000 at 6.5% over 360 months, equal payments, disbursed on January 15, 2026.

A 29-day February in a leap year is about 4.66% below the ÷12 figure. Twelve periods starting January 15, 2026 add up to exactly 365 days, so the first year is almost a wash: $3.37 apart.

1. Annual rate ÷ 12: every month is the same size

Best for: quick estimates, comparing offers, and contracts that state a monthly rate.

Each period is treated as one twelfth of a year no matter how many days it has. On a declining balance, the interest falls a little every month and the principal share rises smoothly:

This is how most loan calculators work, and it is the app's default. It is easy to check by hand and makes two offers directly comparable. If you are new to reading these rows, see how to read an amortization schedule.

2. Actual days ÷ 365: interest follows the calendar

Best for: matching a statement from a lender that charges interest per day.

The annual rate is split into daily interest, and each period is charged for the days it actually contains:

Period 1: 300,000 × 6.5% × 31 ÷ 365 = $1,656.16
Period 2: 299,759.96 × 6.5% × 28 ÷ 365 = $1,494.69

With the payment fixed at $1,896.20, the principal share jumps around:

The disbursement date matters too. Move it to January 31 and period 1 runs to February 28, only 28 days, with $1,495.89 of interest. Period 2 then runs from February 28 to March 31 (31 days) and period 3 from March 31 to April 30 (30 days). When a month is too short for the original day, the app uses the last day of that month.

3. Over the life of the loan: small total, bigger last payment

Best for: understanding why the final payment on your statement may not match the others.

Over 30 years, actual days cost $655.82 more in total, about 0.17%. The extra comes from leap years: seven February 29ths fall inside this loan, and each one adds a day of interest. Take those seven days out of the count and actual days would have cost $299.16 less than ÷12 instead.

Because the app keeps the regular payment at $1,896.20, the extra interest is not charged along the way. It shows up as a bigger final payment: $2,556.73 instead of $1,900.91. Lenders handle this in different ways, so if your final payment or your regular payment differs, ask your lender how they settle the difference.

With equal principal, the principal part stays fixed and the payment itself moves with the days. For $24,000 at 8% over 12 months from January 15, 2026:

Total interest is $1,035.83 with actual days against $1,040.00 with ÷12, about 0.4% less, because the short 28-day period comes early, while the balance is still at its highest. For how this method differs from equal payments, see equal payment vs equal principal.

4. How to switch to actual days in Loan Calculator

Best for: making your saved loan follow the same rule as your statement.

1. Enter the loan as usual on the calculator: amount, rate, term and interest method.
2. Open Advanced options and turn on Charge interest on actual days (365).
3. Tap Disbursement date: today and pick the date the money was paid out. The button then shows "Disbursed:" with your date. If you skip this, the app counts from today and says so: "Counting from today, as no drawdown date is set."
4. Tap Calculate. Under the result you will see a line such as "Worked out as: Equal payments (annuity) · actual days ÷ 365. This is an estimate from the figures you entered; your bank's own schedule may differ."
5. Open the Amortization schedule and compare the interest column with your statement, month by month.
6. Tap Save loan to keep the setting. The day count is stored with each saved loan, so one loan can use actual days while another stays on ÷12.

The same "Worked out as" line appears on the schedule and in PDF and CSV exports, so nobody reading your numbers has to guess which rule was used. The switch is part of the free calculator, and every calculation runs on your phone.

Which day count should you choose?

FAQ

Why is my February interest lower than January's?

With actual days, February has 28 days (29 in a leap year) and January has 31. In the example, the 28-day period cost $1,494.69 while the 31-day one before it cost $1,656.16, even though the balance barely changed.

Does actual/365 cost more than ÷12?

Over a full year of 365 days they come out almost the same: $3.37 apart in the first year of the example. Over 30 years the leap days tip it to $655.82 more, about 0.17%. On a short loan it can even be slightly less, as the equal-principal example shows.

Why does my monthly payment stay the same?

With equal payments, the app keeps the regular payment calculated with the usual formula and lets the interest and principal split change each month. The final payment settles whatever is left, which is why it was $2,556.73 in the example.

What if I don't know the disbursement date?

The app counts from today and adds "Counting from today, as no drawdown date is set." to the result. You can set the date later from Advanced options; the schedule updates when you calculate again.

Can I use actual days with equal principal or flat rate?

Yes. The switch applies to the method selected on the form, and the "Worked out as" line names both the method and the day count so you can see what was used.