How did the term "Rule of thumb" originate and what does it mean?

Answer 1

The wife beating story is bunk and it's believed it actually began with woodworkers using their thumb as a handy reference for an inch from tip of the nail to the first joint.

Answer 2

When you hold your right hand with the fist closed and the thumb raised, the direction of the magnetic field is indicated by the other fingers when the current is flowing in the direction of the thumb.
This is a rule of Thumb!!

Answer 3

I believe it was a unit of measure in Europe hundreds of years ago that was based on the width of the ruling kings thumb.

Answer 4

Interesting..I thought that it came from the ancient roman (?) tradition of putting up or down thumb as a sign of "yes or no", "live or die" when the ruler decided someones destiny?! But that could be just a wild association..

Answer 5

A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. Origin of the term

The term "rule of thumb" or similar stands in many languages and cultures for "quickly understood, easily used, practical method".

Domestic violence/discipline

It is often claimed that the term originally referred to the maximum thickness of a stick with which it was permissible for a man to beat his wife. This explanation for the origin of the term was popularized in the opening of the 1999 movie The Boondock Saints.


Linguist Michael Quinion, citing the research of Sharon Fenick, notes that there are some examples of a related usage historically — most notably with regard to a supposed pronouncement by a British judge, Sir Francis Buller. However, it is questionable whether Buller ever made such a pronouncement and there is even less evidence that he phrased it as a "rule of thumb"; the rumoured statement was so unpopular that it caused him to be lambasted as "Judge Thumb" in a satirical James Gillray cartoon. According to Quinion, the term "Rule of Thumb" was first documented in English in 1692, long before Buller's reported pronouncement. The first known usage of the phrase "rule of thumb" in direct reference to domestic violence was in 1976, in the book Battered Wives by Del Martin.

Use as a physical measurement

The measurement of an inch is derived from the distance between the base of the thumbnail and the first joint. This is a plausible origin as the thumb is often used for rough measurement by carpenters, seamstresses, artists and many others.

The Russian Tzar

The Russian Tzar Alexander II has been suggested as the creator of this term. In an apocryphal story he is said to have drawn the route of a railroad from St. Petersburg to Moscow, accidentally tracing his thumb. The engineers, nervous about disobeying his orders, laid the tracks with an unnecessary curve according to the line drawn.

Used to determine wind direction

A technique for approximating the general direction of the wind involves wetting the thumb then raising it in the air.

Used for plate settings at the Royal table

A technique for setting a row of plates an equal distance from the table edge. Plate setters, setting plates for an English Royal banquet, place the plate against the tip of the thumb while holding the arch of the thumb and first finger against the table edge.

Used to measure the coldness of beer

In England, before the advent of thermometers, bar-tenders used to stick their thumbs in a beer to ensure its coldness. It is also said that it was standard practice at this time to stick one's thumb into the boiled wort to ensure that it wasn't too hot to accommodate the yeast.

Examples of usage

Financial - Rule of 72 A rule of thumb for exponential growth at a constant rate. An approximation of the "doubling time" formula used in population growth, which says divide 70 by the percent growth rate. In terms of money, it is easier to use 72 (rather than 70) because it is easily divisible by 12 (the number of months in a year). Therefore, divide 72 by the percent interest rate to determine the approximate amount of time to double your money in an investment. For example, at 10% interest, your money will double in approximately 7.2 years (72/10=7.2).

Tailors' Rule of Thumb A simple approximation that was used by tailors to determine the wrist, neck, and waist circumferences of a person through one single measurement of the circumference of that person's thumb. The rule states, typically, that twice the circumference of a person's thumb is the circumference of their wrist, twice the circumference of the wrist is the circumference of the neck, and twice around the neck is the person's waist. For example, if the circumference of the thumb is 4 inches, then the wrist circumference is 8 inches, the neck is 16 and the waist is 32. An interesting consequence of this is that — for those to whom the rule applies — this simple method can be used to determine if trousers will fit: the trousers are wrapped around the neck, and if the two ends barely touch, then they will fit. Any overlap or lack thereof corresponds to the trousers being too loose or tight, respectively.

Marine Navigation A ship's captain should navigate to keep the ship more than a thumb's width from the shore, as shown on the nautical chart being used. Thus, with a coarse scale chart, that provides few details of nearshore hazards such as rocks, a thumb's width would represent a great distance, and the ship would be steered far from shore; whereas on a fine scale chart, in which more detail is provided, a ship could be brought closer to shore.

Personal Displays of Affection Also used as a rule to determine how far down in one's pants one's hands may be while in public places. The rule is that one's hands may protrude into one's pants as long as the thumbs extrude from the article of clothing in question.