7-9
  5. Amortization
  This calculator can be used to calculate the principal and interest portion of a monthly 
installment, the remaining principal, and amount of principal and interest repaid up to any 
point.
u Formula
  
  
  
  
  
  
  
  
  
  
  
  
  
   a  : interest portion of installment PM1 ( INT )
   b  : principal portion of installment PM1 ( PRN )
   c  : balance of principal after installment PM2 ( BAL )
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   d  : total principal from installment PM1 to payment of installment PM2 ( Σ  PRN )
   e  : total interest from installment PM1 to payment of installment PM2 ( Σ  INT )
  * 
a  +  b  = one repayment ( PMT )
  
  
  
  
  
  
  
  
  
 
c
a
1 payment
Number of Payments
1 PM1 PM2 Last............ ................... ..........
b
c
a
1 payment
Number of Payments
1 PM1 PM2 Last............ ................... ..........
b
1 payment
Number of Payments
1 PM1
PM2
Last............. ................
.............
e
d
1 payment
Number of Payments
1 PM1
PM2
Last............. ................
.............
e
d
a : INT
PM1
 = I BAL
PM1–1
 × i I × (PMT sign)
b : PRN
PM1
 = PMT + BAL
PM1–1 
× i
c : BAL
PM2
 = BAL
PM2–1
 + PRN
PM2 
d : 
Σ
 PRN = PRN
PM1
 + PRN
PM1+1
 + … + PRN
PM2
e : 
Σ
 INT = INT
PM1
 + INT
PM1+1
 + … + INT
PM2
PM2
PM1
PM2
PM1
a : INT
PM1
 = I BAL
PM1–1
 × i I × (PMT sign)
b : PRN
PM1
 = PMT + BAL
PM1–1 
× i
c : BAL
PM2
 = BAL
PM2–1
 + PRN
PM2 
d : 
Σ
 PRN = PRN
PM1
 + PRN
PM1+1
 + … + PRN
PM2
e : 
Σ
 INT = INT
PM1
 + INT
PM1+1
 + … + INT
PM2
PM2
PM1
PM2
PM1