[Bell Historians] Conversions

Carl S Zimmerman csz_stl at ...
Thu Oct 13 21:18:44 BST 2005

Peter Rivet wrote, "For general purposes, to get an approximate 
figure, it helps to know that 10cwt is 509kg. ... Obviously as they 
are conversions if the imperial figure is an estimate, the metric 
equivalent won't be accurate to the exact kilogram." That's a very 
good point, and one that we often forget in translating from the 
customary sloppiness of the spoken word to the apparent exactness of 
the written word. While it's been discussed before, it bears 
repeating now.

"10cwt is 508kg" is only true if qualified with "exactly", i.e.,
"exactly 10 cwt" is 1120.000 lbs, which is 508.023 kg.

But "10 cwt" is 1120 +/- 56 lbs, which is 508 +/- 25 kg;
a good way to state this in conversation would be
"10 hundredweight is a bit more than 500 kilograms."

Even better:
"An Imperial ton is just about the same as a metric ton."
(Imperial ton = 2240 lbs = 1016 kg = 1.016 metric tons,
so "just about the same as" means "within 2% of" in this context.)

More details about weights and conversions can be found at
(my thanks to Chris Pickford for his kind words in referencing this)
and at
(which has conversion tables).

Carl Scott Zimmerman, CCP
Certified Computing Professional (ICCP) and Campanologist


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