This program is Copyright © 1974 by HewlettPackard and is used here by permission. This program was originally published in the HP65 Standard Pac.
This program is supplied without representation or warranty of any kind. HewlettPackard Company and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.
Loan Repayment 

Label 
Years ^
per/year 
i% 
PV 
PMT 
Calc(P) 
Key 
A 
B 
C 
D 
E 
Given the term for a direct reduction loan in years, the number of periodic payments per year, and the annual interest rate in percent this program computes:
1. Periodic payment amount, if the principal value borrowed is given.
or
2. The principal value if the periodic payment is given.
A one half cent roundoff routine is incorporated so that the answers are correct to the nearest cent.
PV = PMT * [ ( (1+i/(100*n))^{yn}1 ) / ((i/(100*n))*(1+(i/100*n))^{yn} ) ]
where:
PV = Principal value
PMT= Periodic payment
i = Annual interest rate in percent
y = Number of years
n = Number of payment periods per year
Step 
Instructions 
Input Data/Units 
Keys 
Output Data/Units 
1 
Enter program 

2 
Input number of years 
y 
ENTER 
y 
3 
Input payment periods/year 
n 
A 
yn 
4 
Input annual interest 
i(%) 
B 
100 
5 
Input either principal value 
PV 
C 
PV 

or payment 
PMT 
D 
PMT 
6 
Calculate either 



6 
payment 
E D 
PMT 


or principal value 

E C 
PV 
7 
Perform steps 2 & 3, or step 4  
8 
or step 5 for new values. 



Note: Unrounded values for  
PMT or PV calculations are  
stored in register 8 after  

calculation 



Find the quarterly payment for a thirty year mortgage at 8.75% with a principal amount of $37,500. Key 30 and press Enter, then key 4 and press A to set up quarterly payments on a 30 year loan. Key in the interest rate of 8.75 and press B. Key 37500 and press C. To calculate the payment, press E and then D and the answer of 886.36 is displayed.
What principal value exactly corresponds to the payment just calculated? Press D to input the payment still in the x register. Press E and then C to calculate the exact principal of 37499.86.
What would the payment be if the interest rate was 9.25%? Key in 9.25 and press B. Press E and then D to calculate the new payment of 926.83.
At this new interest, what would the payments be if they were made monthly instead of quarterly? Key in 30 and press Enter and key 12 and press A to set up monthly payments. Then press E and then D to calculate the payment of 308.50.
CODE KEYS 23 LBL 11 A 33 07 STO 7 71 x 33 01 STO 1 24 RTN 23 LBL 12 B 33 02 STO 2 43 EEX 02 2 33 05 STO 5 24 RTN 23 LBL 13 C 32 f^{1} 71 SF 2 31 f 61 TF 1 22 GTO 01 1 33 03 STO 3 24 RTN 23 LBL 14 D 31 f 61 TF 1 22 GTO 01 1 33 04 STO 4 24 RTN 23 LBL 15 E 31 f 51 SF 1 31 f 71 SF 2 24 RTN 23 LBL 01 1 32 f^{1} 51 SF 1 34 02 RCL 2 34 07 RCL 7 81 ÷ 34 05 RCL 5 81 ÷ 01 1 61 + 34 01 RCL 1 35 g 05 y^{x} 33 06 STO 6 01 1 51  34 06 RCL 6 81 ÷ 34 07 RCL 7 71 x 34 02 RCL 2 81 ÷ 34 05 RCL 5 71 x 32 f^{1} 81 TF 2 22 GTO 03 3 34 03 RCL 3 35 07 g x<>y 81 ÷ 22 GTO 04 4 23 LBL 03 3 34 04 RCL 4 71 x 23 LBL 04 4 33 08 STO 8 21 DSP 83 . 02 2 34 05 RCL 5 71 x 83 . 05 5 61 + 31 f 83 INT 34 05 RCL 5 81 ÷ 84 R/S 35 01 g NOP 35 01 g NOP 35 01 g NOP 35 01 g NOP 35 01 g NOP 35 01 g NOP 35 01 g NOP 35 01 g NOP
R1 yn R2 i R3 PV R4 PMT R5 100 R6 (1 + i/100)^{yxn} R7 n R8 PV or PMT
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