Due to the beta state of this site and its use of English only, most questions and answers use United States customary units, particularly inch and feet, but also gallons and degrees Fahrenheit (the latter already has been in question).

For the average US citizen that might be alright, but since they’re the only ones stuck in that ancient “system”, it’s always a hassle converting to SI units.

I recently suggested such an approved revision and was about to do so again, but I think it’s a fundamental decision best determined on Meta.

Should US units always be supplemented by SI units?


  • 20 ft x 3 ft (ca. 6×1 m)
  • 1.5"-2" (3.81–5.08 cm)
  • 20 gallon (about 75 liters)
  • 100–110°F (~38-43°C)

For non-native speakers, it’s notably harder in terms of gardening than, for instance, regarding computer science.

It’s not just recognizing the physical quantity and converting the unit, but also rounding the result: An easy “100-110 °F” would be between 37.777… and 43.333… degrees centigrade, and obviously a notation of “38-43 °C” would be more than inaccurate.

  • I don't have time to write a coherent answer, so I'll just leave a comment to thank you for bringing this up. I'm an American stuck in the ancient system, and since many of our most prolific posters come from elsewhere, I always have to keep my handy "conversion chart" page open, but from the other perspective. I'm all for offering both measurements, and would appreciate and approve any edit that added the information. I've done it myself with temperatures. I'll be interested to see how others feel. Commented Mar 29, 2016 at 0:19
  • @Sue, thanks for sharing your thoughts, you definitely should consider adding an extensive answer ;-) I think it’s perfectly okay for people to use those units they’re comfortable with. I’d gladly add int’l units silently afterwards, but rather do it according to an established agreement.
    – dakab
    Commented Mar 29, 2016 at 9:58

6 Answers 6


I'm going to contradict the other answers here: Personally, I'm from Europe and all measurements here are in SI units (apart from PC/phone/TV screen sizes), so I'm really NOT familiar with imperial units. It is pretty annoying to have to open a unit converter every time some measurement of interest is given in an answer or a questions.

Since (as David Richerby stated in a comment to Graham's answer) only about a third of all users is American, I would expect quite a few people to have the same problem. So I would say: Go for it, and add SI units! I certainly will be grateful.

  • 2
    I think I could write a bot to do this ... Commented Apr 4, 2016 at 10:32

I live where we buy wood in inches and feet and food in kilograms or grams so I am familiar with SI shyness. I have added both units in answers if I have time and hope others will follow suit.


I use SI units at home but tend to post here in imperial measurements since the majority of participants here are familiar with that system.

I think it's a translation issue, and as long as we post the units, SEX should be able to convert them to our chosen locale rather then force everyone to post units twice.

In fact I have written a script that parses out units and converts them for scientific papers.

Edit: I've posed the question on Meta Automated unit conversion based upon user locale

  • Is SE able to auto-convert units somehow (like running your script on marked-up units)? People don’t have to post both units when editors are engouraged to add them later. And since only the US, Myanmar and Liberia are not using metric, US readers are not in majority (at least on SO).
    – dakab
    Commented Apr 1, 2016 at 17:45
  • No, it isn't but that's something that could be discussed on meta. The majority of posters here seem to be from the USA. Commented Apr 1, 2016 at 20:49
  • oh well, it's not being received well. If you like or dislike the idea, at least on this site, then vote meta.stackexchange.com/questions/277828/… Commented Apr 1, 2016 at 22:46
  • 1
    "I [...] post here in imperial measurements since the majority of participants here are familiar with that system." Are you sure? Only around a third of Stack Overflow users are American (plus, presumably, a negligible number in Liberia and Burma). Commented Apr 3, 2016 at 7:54
  • 1
    @david_richerby I'm going on what I see posted in gardening on a regular basis. Stackoverflow is quite a different audience. Commented Apr 3, 2016 at 8:12

Unit conversion is sufficiently available that I don't think it's worth editing in. If you're answering it's definitely fine to present both, though it would probably be most useful to make sure you include US measures (British really) as SE sort of has an assumed default of American English.

  • 1
    English as a language, but not to suit Americans, but to satisfy an international audience. Is there a reference for US customary units assumed a (SE) rule? Surely anybody could copy units to a conversion calculator, but that doesn’t improve the actual question/answer for the vast majority (95+% world, 63+% SO users) of the readership.
    – dakab
    Commented Mar 31, 2016 at 18:38
  • 1
    "US measures (British really)". No, they're American. American liquid measures are significantly different from the British, as is the hundredweight (though I guess that doesn't come up nearly as often). And the UK is mostly metric, these days. A default of American English has nothing to do with what units should be used. Commented Apr 3, 2016 at 7:50

SI units are the international standard. You should include them. Rounding to "reasonable" ranges is fine. No one is going to call you out if you say 1-2" (2-4cm) - unless you the precision does matter, at which point you should use significant figures to specific.

1 is generally assumed to be 0.5-1.49. But 1.00 is better 0.995 and 1.0049

For gardening, such degree of precision is rare I find.


It's easy to convert from either. While I use SI in general, I find myself often mixing the two in day to day gardening. A foot spacing, or a half inch fingernail depth for larger seeds, are quite ubiquitous, as is a foot's growth a year, I know it's 30cm but a foot just rolls off the tongue.

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