Example 1
- Amount: 5,000
- Rate: 10% annual
- 30 days, actual/365
Interest ≈ 41.10
Daily ≈ 1.37
Simple estimate: 5000 × 0.10 × (30/365).
Default interest calculator
The default interest calculator uses simple late interest from an amount, an annual rate, and a day count. 5000 at 10% for 30 days on actual/365 is about 41.10, or about 1.37 a day. You type the rate; the calculator does not insert a statutory rate.
Interest ≈ amount × rate × (days ÷ 365 or 360). 5000, 10%, and 30 days yield about 41.10. This is not an installment and not a repayment schedule.
Results
Overdue amount, Annual interest rate (%), Delay length (days) and Start date (optional). The result shows up here.
How results are calculated
Default interest on this page is a late-payment sketch: amount times (rate/100) times days divided by a year base. The base is actual/365 or 30/360, chosen with a radio, not typed as a number. There is no compounding. The result depends on the rate you type. Statute, contract, and local rules can differ; this is not legal or bookkeeping advice.
The first card uses 5000, 10%, and 30 days on actual/365 and yields about 41.10 of interest and about 1.37 a day, because 5000 × 0.10 × 30/365. Amount due is the principal plus that interest. Instead of typing days you can give a start date and an end date; with both dates the calculator counts the span. Scenario B compares a different day count or rate on the same amount.
Type Overdue amount, Annual interest rate (%), and Delay length (days), or leave days blank and fill both dates. Choose actual/365 or 30/360. Dates and scenario B sit under extra options. Click Calculate and read estimated interest plus the total due.
Paying a balance down in installments lives on other loan pages, not here. Household budget shows whether the month even has a surplus for this arrears. This calculator stays with one delay and one or two rates.
41.10 at 10% is not a court award. Another year base, contractual compounding, and a partial payment along the way will move the figure. Scenario B does not handle installments mid-span.
Type 5000, 10, and 30, leave actual/365. Check about 41.10. Then switch 30/360 to see how a 360-day base lifts the same month.
How to use
- In Overdue amount, type what is unpaid, for example 5000. In Annual interest rate (%), type the rate, for example 10.
- In Delay length (days), type days, for example 30, or leave it blank and enter both dates under extra options.
- Choose actual/365 or 30/360. That is a radio, not a number field.
- Optionally type scenario B: different days and/or a different rate on the same amount.
- Click Calculate. At 5000, 10%, 30 days, and actual/365, interest should be about 41.10.
Actual/365, 30/360, and late interest
Simple late interest: amount × rate × (days ÷ 365 or 360). 5000 at 10% for 30 days on actual/365 is about 41.10, or about 1.37 a day.
- actual/365
- Calendar days over 365. 5000 × 0.10 × (30/365) ≈ 41.10. Not an installment and not 30/360.
- 30/360
- Bank convention: 30-day months, 360-day year. On 8000 at 10% for 60 days it uses 60/360, not 60/365.
- interest
- The late-interest result. 41.10 from 5000 / 10% / 30 days. You type the rate; the calculator does not insert a statutory rate.
Examples
Example 2
- Amount: 12,000
- 11.25% annual
- 2026-01-01 to 2026-03-15
Days from date range
Interest via actual/365
Instead of typing days by hand.
Example 3
- 8,000 @ 10%, 60 days (30/360)
- B: 90 days @ 12%
Compare Δ interest
A vs B
Same amount, different time/rate.
Example 4
- Overdue amount: 5,000
- Annual interest rate: 10%
- Delay: 30 days, actual/365
Interest ≈ 41.10
Daily ≈ 1.37
What does actual/365 do with 5,000 at 10% for 30 days? About 41.10. 30/360 would divide those 30 days by 360.
Example 5
- Overdue amount: 5,000
- Annual interest rate: 11.25%
- Delay: 14 days, actual/365
Interest ≈ 21.58
How much is 14 days versus 30 days on 5,000 at 11.25% actual/365? About 21.58 for 14 days. 30 days is about 46.23.
Example 6
- Overdue amount: 5,000
- Annual interest rate: 11.25%
- Delay: 30 days, actual/365
Interest ≈ 46.23
What does 5,000 × 0.1125 × 30/365 come to? About 46.23. Rate on the page is 11.25, not 0.1125.
Example 7
- Overdue amount: 5,000
- Annual interest rate: 11.25%
- Delay: 30 days, 30/360
Interest ≈ 46.88
Does a 360-day year raise the 30-day charge on 5,000 at 11.25%? Yes. 30/360 is about 46.88, actual/365 is about 46.23.
Related calculators
FAQ
How much default interest is 5000 at 10% for 30 days?
On actual/365 about 41.10, about 1.37 a day. 5000 × 0.10 × 30/365.
How does 30/360 change those same 30 days?
A 360-day base raises the year fraction. The same 10% and 5000 will come out a little above 41.10.
Do I have to type days if I have dates?
No. With both dates the calculator counts the span (or 30/360 from the dates). You can leave days blank then.
Does the calculator insert a statutory rate?
No. The result depends on the percent you type. 10 in the example is your number, not a statute.
How is this different from a loan installment?
Here one delay and simple interest. An installment and a schedule pay principal down over time, with a different formula.
Why is there a scenario B?
To compare another delay or another rate on the same amount. No partial payment along the way.
Does the interest compound?
No. The formula is simple. Contractual interest-on-interest is not used here.
Is 41.10 legal advice?
No. It is an educational estimate. A statute, a contract, and a court may count differently.
How do I price 60 days on 30/360 from 8000 at 10%?
8000 × 0.10 × 60/360 = 133.33. That setup is on the third card, next to a scenario B comparison.
Can I add VAT to the interest?
Not on this page. Invoice VAT lives on the VAT calculator, with a different rate and direction.
Knowledge sources
Default interest is amount × rate × days/365 or 360. You type the rate; this is not a statutory table.
Page updated in 2026.