Following is a “quick reference” showing the formulas used by CU*BASE when calculating interest for loan accounts.
· Click here for dividend calculation methods for savings and certificate accounts.
The standard daily interest calculation using a 365 or 366day year. Not for mortgagetype loans. Interest is accrued each day using a Daily Interest Factor (per diem).
Interest Rate 
÷ 
Day In Year 
= 
Daily Interest Factor 
xx.xxx 

36500 (nonleap year) 

.xxxxxxxxx 


36600 (leap year) 


Daily Interest Factor 
´ 
Current Balance 
= 
Daily Interest Amount 
.xxxxxxxxx 

Xxxxxxx.xx 

xxxxxxx.xx 
Daily Interest Amount 
´ 
No. days since last calc. 
= 
New Interest Amount 
xxxxxxx.xx 



xxxxxxx.xx 
Sample: 
12.50 ÷ 36500 = .000342465 

.000342465 ´ 2500.00 = .86 

.86 ´ 1 = .86 
SEE ALSO: CU*BASE Mortgage Products: 360Day Interest Calculation
Loan origination will not calculate short interest. Interest due is left equal to zero.
Monthly calculation of interest is in arrears. On the 20th of each month if interest due is equal to zero, then the current month's interest is calculated and added to interest due.
If the interest due is not equal to zero on the 20th of the month, then the system will monitor interest due every night and calculate the current month's interest when it becomes zero, or on the 1st of the next month, whichever occurs first.
If the current balance is greater than INTBAL on the account on the day that interest is being calculated, then INTBAL is set equal to the current balance. Otherwise, the INTBAL is equal to last month's INTBAL minus last month's principal payment amount.
Interest Rate 
÷ 
1200 
= 
MNTRAT 
Xx.xxx 



??.xxxxxxx 





INTBAL 
´ 
MNTRAT 
= 
NEWINT 
xxxxxxxxx.xx (rounded) 

??.xxxxxxx 

??.xx 
The interest due on the account is adjusted by adding this NEWINT to the existing amount.
A new INTBAL is calculated and stored on the account using the following calculation:
Fixed Payment 
 
NEWINT 
= 
PRINCP 


??.xx 

xxxxxxxxx.xx (rounded) 




If less than zero, change to zero. 
INTBAL 
 
PRINCP 
= 
INTBAL 
xxxxxxxxx.xx (rounded) 

xxxxxxxxx.xx 

xxxxxxxxx.xx (rounded) 


If less than zero, change to zero. 


This calculation acts like a 365day simple daily calculation but looks like a 360day calculation where each month has only 30 days. Like the simple 365day interest calc. type, this method calculates interest accruals every day using a daily per diem interest amount. But instead of using 365 or 366 days when figuring the daily interest amount, the rate is always divided by 360 days.
Interest Rate 
¸ 
360 
´ 
Loan Balance 
= 
Daily Interest Factor 
xx.xxx 





.xxxxxxxxx 