HP15c program: Generic unit conversion

command         display

f LBL A      001-42,21,11   // LBL A 
   RCL 0      002-   45  0
     ÷        003-      10
g RTN        004-   43 32
f LBL B      005-42,21,12   // LBL B 
   RCL 0      006-   45  0
     *        007-      20
g RTN        008-   43 32

This program uses the following labels: LBL A (remember: A=divide), LBL B (remember: B=multiply)
mnemonic trick: you calculator has at the top the divide key and below the multiply key. A comes before B in the alphabet.
This program uses STO 0 to store the conversion constant.

Using the program

A lot of unit or currency conversion can be done simply by multiplying or dividing with a conversion factor. This program uses a generic conversion constant stored in register 0 (STO 0). It is a very simple but useful program that I use frequently.

I start every program with a label. This way you can have a number of programs in your 15c and you just select which one to run by pressing f LABELNAME (f A or f B in this case) or GSB LABELNAME (GSB A or GSB B in this case).

Let's assume you are working on the design of a printed circuit board and you need to convert frequently between mm (millimeter) and mil (1/1000 of an inch).

The conversion factor from mil to mm is therefore: 0.0254 mm/mil
Store this factor in register 0: 0.0254 STO 0

To convert now 5mm into mil you type: 5 f A
The result should be 196.85mil

To convert now 100mil into mm you type: 100 f B
The result should be 2.54mm