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The width of the Voyagers, in decimal inches, is remarkably close to pi. From the picture:

        width = 3 + 2/16 + 2/128 = 3 + 18/128 = 3 9/64" = 3.140625"

width = 7.98 mm = 7.98/2.54" = 3.1417"

Geek designer or coincidence? :-)

Olá Gerson,

IMO you must decide first which of both indicated values you want to believe in - the upper (indicated in Imperial English Thumbs) or the lower (indicated in mm)? Then please repeat your measurement a few times (no cheating!) to gain a feeling for your standard deviation. If you've got more than one Voyager, measure them all to gain a feeling for their standard deviation. Then return and renew your claim.



Hallo Walter,

The first value was read on the Vernier inch scale and the second one on the millimeter scale. The latter should be more accurate, since the divisions are closer to each other. Anyway, what I can read is 3 9/64" and 7.98 mm, which are equivalent to 3.14" (with three significant digits at most -- the value 3.1417 was fanciful, of course). I measured two HP-15C units (from 1983 and 1989, respectively), having found the same results (both definitely greater than 3 1/8"). But you're right: more measurements should have been made. Also, perhaps I should use a decent instrument instead of this cheap one (Made in PRC :-)



Edited: 12 Dec 2012, 11:22 p.m.

Would this convince the skeptical? :-)

HP-16C   2403A02548  3.1415
HP-15C 2343B75099 3.1415
HP-15C 2905B29505 3.134
HP-12C CN04808261 3.1345
HP-11C 2540B16771 3.1345
HP-12C+ CNA83816873 3.133
HP-15CLE CNA13207R7 3.1405

Cm and not mm.
The caliper is in cm and the calculator is 79.8 mm.
One inch is 25.4 mm or 2.54 cm.

Please bid on the next Texas Instruments TI-1890. No enter key but 20 metric conversions built in.


It clearly shows you can tilt a caliper in a way it indicates 3.1415".


Cm and not mm.

I see now the mistake has been repeated in my first reply to Walter (m is not close enough to c so I can call it a typo :-).



Despite Gerson's Law, no tilting and no data manipulation :-)

The golden ratio form factor of the Voyagers is well known:

lenght/width = 128.46 mm / 79.76 mm = 1.611 (~ phi)

Thanks for the pointing out your discovery. So in addition to being the golden ratio of length:width, the calculator is around Pi inches in width.

One day maybe someone will make a smart phone with these appealing dimensions.

Perhaps, if you fitted the callipers on `blind' (read-out hidden or off) with measurements across samples, as well as replicates on each calculator, this would allow a better estimate of the width that allows for variance components due to both sampling and measurement error. That might just convince a sceptic...


According to this article, the dimensions of the plastic ABS case are 5 x 3 1/8 x 5/8 inches. On the other hand, regarding the HP-15C LE HP says they are 12.9 x 8.0 x 1.52 cm (5.1 x 3.1 x 0.6 inches), or 5.08 x 3.15 x 0.60 inches, assuming the cm dimensions are correct.



The width of the 42S is pretty close to that too...

I like to think it is not a coincidence :-)

The width of the 42S is pretty close to that too...

You're right:

HP-42S   ID939005390 3.144"
HP-42S 3132B19700 3.143"
HP-32SII 3533S00038 3.149"
HP-17BII 3518S07942 3.149"

I like to think it is not a coincidence :-)

Perhaps someone with access to more precise instruments (and better measuring technique) could confirm this :-)