[pdxuser]

There are 1.59 grams of sucrose in a cubic centimeter.

The relative density/specific gravity/experimental gravity of sucrose is listed online as 1.58 g/mL, 1.580, 1.5805, 1.587 g/cm³, 1.587, 1.5877, 1.588, 1.59, 1.59 kg/L, and 1.59 kg/L. (1 g/cm³ = 1 g/mL = 1 kg/L.) Rounding the average would result in a value of 1.59 g/cm³.


Online converters all agree that, rounded to the nearest hundredth, there are 4.93 cubic centimeters in a US teaspoon (A,B,C), 5.00 cubic centimeters in a metric teaspoon (D,E,F), and 4.74 cubic centimeters in a Canadian teaspoon (G,H,I). Some sources say there's 3.55 cubic centimeters in a UK teaspoon (J,K,L), while others say there's 5.92 (M,N,O). Since my other sources are American, I'll go with US teaspoons.


Table sugar is sucrose. US federal regulations say that, "For purposes of ingredient labeling, the term sugar shall refer to sucrose."


Government and university sources say there are 4.2 grams of sugar in a teaspoon (A,B,C), while news articles and consumer-oriented health sites say there are 4 grams in a teaspoon (D,E,F). This article from Michigan State University says that "4.2 grams equals a teaspoon, but the nutrition facts round it to four grams."


But if we multiply the 1.59 grams of sugar in a cubic centimeter by the 4.93 cubic centimeters in a US teaspoon, we get 7.84 grams of sugar in a teaspoon. I would have to take my result and divide by 1.87 to get the consensus result. The disputed UK teaspoon volume of 3.55 cubic centimeters doesn't solve the issue. Not only are these US sources that wouldn't be using UK teaspoons, but if you do use that measure for UK teaspoons, the result is still off by 1.34 times (5.64 grams vs. 4.2 grams).


For comparison, I looked at salt, and I came to a similar result: With 2.17 grams of sodium chloride in a cubic centimeter, and 4.93 cubic centimeters in a teaspoon, I would expect (2.17 * 4.93 = ) 10.70 grams of sodium chloride in a teaspoon. But the consensus is 5.69 grams of sodium chloride in a teaspoon. (Careful: Don't confuse sodium and sodium chloride. Most sources give the mass of sodium, not sodium chloride, in a teaspoon of table salt.) I would have to take my result and divide by 1.88 to get the consensus result.


So, my question is, why are these calculations resulting in a value that's 1.87 to 1.88 times larger than the consensus?

[Yggdrasil]

You calculations assume that the teaspoon is a solid block of sugar.  You probably lose a considerable amount of volume to empty space when you have a teaspoon of sugar crystals packed close to each other.

Indeed, recipies for salt often call for different volumes depending on the shape of the salt (e.g. the more cubic table salt vs the flatter kosher salt crystals). 

[Arkcon]

I don't know.  I never took the measurements to be as exact as you have, so it never worried me.  I don't know how accurate the first list of values can be Accurately determining the volume of a pile of granular crystals, that seems like a measurement that could have many pitfalls.

I don't know how good the various online metric converters are, and again, I don't know how accurate measuring with teaspoons is.

You seem angry, with your list of sources and switching to red for emphasis.  I thought I'd point that out right away.  I don't really know what to make of it all, except that teaspoons isn't an accurate measurement.  No manufacturer uses them when making some product, so I can't see it as particularly significant.

[Borek]

For calculations of the weight of sugar measured with a spoon you need to use http://en.wikipedia.org/wiki/Bulk_density

[pdxuser]

I highlighted the core points just because the post was a bit lengthy and technical. Thank you for the info on bulk density!