Rule of thumb comes from the days before standardised measuring units. The thumb is the most useful digit for measuring as it is similar to the distance that became "The Inch" (my thumb is about 2.5") It should be noted that because it is an arbitrary figure, that is my thumb is not the same size as your thumb, my hand made thingummy will not be the same size as your hand made thingummy but the two should be in proportion. the average value for Rule of thumb will vary from race to race as an aside the biblical measurement "The cubit" is the distance from the elbow to the tip of the longest finger. which will again vary from race to race.
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the earliest known written occurrence of the expression was in 1692 when it already meant some method or procedure based on practical experience & without any formal basis
my guess is the expression referred originally to the natural measuring rule for gauging distance from any seen object
which calls for holding a thumb out at arms length against the distant object
& then multiplying by 10 the horizontal distance the thumb appears to jump when viewed from alternately blinking eyes
&
as suggested above
there are a variety of almost as commonly applied measuring rules involving the thumb
which perhaps compete with this rule
or perhaps all together support it
both in its figurative sense as a law or principle & in its earlier literal sense as a physical ruler or measuring device
a british judge sir francis buller was reputed to have said that a man can legallly beat his wife with a stick no thicker than his thumb. but this is a disputed fact.
"Rule of Thumb" means a rule or principle that provides guidance to appropriate behavior.
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The octet rule is a simple chemical rule of thumb that states that atoms tend to combine in such a way that they each have eight...
Rule of thumb is 10' per storie.
Rule of thumb... about half. Approx 2cm to 1inch
It means something that is approximate, something that may be based on experience or general practice. The origin is the 15th Century when measurements were roughly made by using the thumb as a guide
"Rule of Thumb" means a rule or principle that provides guidance to appropriate behavior.
The rule of thumb is not intended to be accurate or reliable for every given situation. When a person is doing something by the rule of thumb, they are taking an educated guess.
what does the phrase rule of thumb mean
Rules of thumb
A misspelled "Rule of Thumb"
If you mean what is the "Rule of Thumb" it is an old law that states a man may beat his wife with a switch, (branch, stick), no bigger around than his "thumb". And we think we are civilized!?! This is completely wrong. There has never been any such law. The urban legend stems from a court case (not a law) in which the phrase "rule of thumb" never even appears. The judge only mentions that "moderate chastisement" of a wife by her husband is not criminal. Not at all excusable, and the judge was publicly excoriated for his ruling at the time. But this is not the origin of the "rule of thumb." The phrase "rule of thumb" comes from woodworkers using the length of their thumbs for measuring instead of using rulers, and it has been in use at least since the 1600s, long before the supposed "law" about wife-beating. A "rule of thumb" is a convenient approximation.
Perhaps you're thinking of the phrase, "rule of thumb".
A useful principle but not intended to be reliable in every situation. Meaning the situation applies to everything because long ago the rule of thumb meant 1 inch equals your top of your thumb, so thats the rule of thumb. Over the years it has taken a more figurative meaning.
The general rule of thumb is that you should be able to see the tires of the car in front of you touching the pavement.
there was a time when 1 inch was the 'rule of thumb' probably 25mm now
In the early centuries it was acceptable for a man to hit his wife if she did something wrong. In order to rule the beating as non abusive, the husband had to use a stick that was no bigger than his thumb. That then gave way to the term, "rule of thumb."