Conversion errors

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Janet Yang on 26 May 2014 at 10:57

I was looking up the number of grams in ¾ cup of sugar, and found a table with some errors. It's at 

http://www.pastryscoop.com/category/look-it-up/sugar/

It says

1/3 cup = 4 1/2 ounces = 150 grams;  3/4 cup = 5 1/4 ounces = 170 grams;  2 cups = 1 pound = 500 grams 
but should be
2/3 cup = 4 1/2 ounces = 133 grams;  3/4 cup = 5 1/4 ounces = 150 grams;  2 cups = 17 1/4 ounces = 400 grams 
Their email address doesn't work anymore, so I couldn't send them the corrections. Janet

Well, perhaps, but how do you sugarcoat it when someone rams through what is probably the most important metric/imperial conversion, that is 1lb = 16oz = 454g?  More importantly, why would you want to?

Hm, 4.5 ounces is 133g and not 128g?

17.25 ounces are 489g and therefore colser to 500g than to 400g.

Wolframalpha gives me 134g for 2/3 US-cups and 129g for 2/3 Canadian cups.

... well?

You're right about the rounding…I should not have allowed the doubling, as it multiplies the error.

The conversion factor varies according to the density of the substance. The conversion factor for granualated sugar is 0.02510792670681. The conversion factor for pure water is 0.02957352969, which is different from the one you are using, but I don't know why.

 

@Janet Yang:

It would be best for you to find recipies that list the ingredients using both weight and volume.  Weight, however, is a more accurate measure for ingredients as volume can change with changes in temperature.  Just ask any chemist.

Best  8)

reason to weigh ingredients, changes in volume are of course existent, but negligible. The real reason is that flour density varies due to the fineness of the grind, scooping method into the measuring cup and so on. Just compare how much does a cup of sifted cake flour weigh and bread flour straight from the bag.

YES, Janet Yang.  It's called STP, standart temperature and pressure in the chemistry field.

This whole thread can be avoided if you adopt metric weights as your standard of measurement.  Avoid volume measurements as volume and therefore density varies with temperature.  Screw the British standard of measurement which is termed avdp, avoirdupoids, meaning to have weight.  The AVDP relies on sixteenths, real confusing cr*p imho and I possess almost four years of college chemistry coursework.

In other words get youself a digital scale.  I use the MyWeigh KD8000 and it's exact and correct in terms of weight measurement right down to the gram.

However, I was using a recipe from the 8th Pillsbury Bake-Off, which called for 3/4 cup of sugar. Of course it would have been easy to use measuring cups, but I wanted to know the exact measure in grams, just for the record. That's how I came across the "3/4 cup = 170 grams of sugar" on that old website.

The density of flour, MisterTT, can vary due to humidity and flour type and whether one fluffs it prior to scooping.  And how long it's sat in the bag. 

Officially, I am led to believe, a US Cup is 240ml (or 8.45 imperial fluid ounces.) This is slightly different from an Australian, Canadian and South African Cup which is 250ml. In the UK I think it is 284ml.

I guess that as long as you use the same cup for measuring out each of your ingredients, the proportions should work out the same using another country's recipes/cups.

I prefer to weigh things in grammes as I think they are the same worldwide - Am I correct?.

Brian

Brian, YOU are correct.  Grams are the same worldwide whereas volume measurements in terms of cups are not.  Weight supersedes all.

Overall I'm amazed at how much input everyone has on this. Not to mention the extent of knowledge on a subject such as units of measure. Really makes me happy to be a part of this community.

That's how I memorized it in Home Ec. It's an easy alliteration to remember, but evidently not quite accurate. "A pint's a pound" means a gallon is 8 pounds, but my resident (former) engineer insists that a gallon is 8.34 pounds.

This reminds me of a book on making chain-mail jewelry. I was having trouble getting the patterns to work, and finally discovered that the wire gauges were wrong. I wrote to the author and It turned out the book used British wire gauges instead of the U.S. wire gauges she had specified. 

I do wish we would convert to the metric system!

For the first 10 years that I baked bread I struggled when it came to rescaling recipies using those darned cup measurements; rescaling by weight and percentages is much much faster .  And since I got my digital scale, I never looked back at using my cups; and, I'll reiterate, weighing stuff takes much less time than using volume measurements.

I always weight out Ingredients , in Germany we do not have Meassuring Cups and / or Spoons.

To weigh out Ingredients is the most accurate way of doing it.

The metric systeme is what I grew up with and the easiest to work with.

The only time I do use cups * normal cups no meassuring cups *is when I make rice.

1 Cup of rice for 2 Cups of water.

I was told by one Lady that she would NEVER use scales as it is to complicated , and that was the Lady that often complained that her cakes and baked good always varied from dense to light even though she used the same recipe.

Pues, no. Most is specified by weight. But then there still are the "teaspoons". And as there is no official volume for teaspoon, percentages really can get off. Some recipes use "heaped teaspoons" some not.

Yes Bob Marley, almost all are done in weight, but as adri said, there are teaspoons for example.

Using a teaspoon is not to bad though, we do have teaspoons and spoons and tablepsoons.

When it comes to heaped teaspoons it is just what it is and one can not get to wrong with it.

Here in the UK people mostly use the metric systeme now , but , like my Mother in Law, she still uses ounces and fluid ounces..

 

I have very different types of teaspoons.

I just picked 2 randomly: One gave me 81g for 10 heaped ones. The other one gave me 96g.

This is 18.5% more.

 

Measuring in weight, I actually don't care, if the recipe is in gram, stone, ounces or bakers-%. As long as it is always the same unit. I always just use the proportions. Only sometimes, when I make something in pans that have to be filled exactly, I need an anchor point.

Adrian

1 Tsp and 1 Tbsp for Sugar would be.

1 tsp = 5g

1 Tbsp = 15g

 

But there are so many things that tsp and tbsp are used for and than those numbers do change A LOT.

http://www.chefkoch.de/magazin/artikel/500,2/Chefkoch/Loeffelmass-in-Gramm.html

I am sorry , this is a German chart.

EL = tbsp

TL = tsp

None of those numbers are for heaped spoons.

The first number is always for the tsp and the second number for the tbsp

At the bottom are some more meassurments with tbsp and tsp.

So I just do what the recipe says and use 1 tsp of this or that or one tbsp of this or that.

If they want to be precise in the recipe they need to give us grams so that we can weigh. sighhhhh

I always use a normla tsp and a normal Tbsp, not had any problems with it , yet.

 

Did you know that the proportion of rice to water varies? The longer the time since harvest, the drier the rice gets and the more water it absorbs. I have never found the difference worth dealing with, though.

Did you know that the proportion of rice to water varies? The longer the time since harvest, the drier the rice gets and the more water it absorbs. I have never found the difference worth dealing with, though.

Oh , I was not aware of this, I must say, the method one cup rice to 2 cups of Water have always worked for me, I never saw a difference.

A european teaspoon messurment ( not a real one) is  5 ml  and an American is about 4.9 mL

moisture and need less water during a rainy season.  One of the reasons kernels of rice are added to salt shakers is to prevent the salt from clumping when the salt attracts moisture.  

I tend to use less than 2 cups of water for 1 cup of white rice because I wash the rice first.  :)

My husband does the rice washing, I just do the 1:2 ratio and so far it worked fine, maybe I am just lucky.

I also never do what it says on the Label, I cook all rice the same.

I put the Water in , salt, brint it to the boil, put the rice in, bring back to a boil , turn the heat on very low, lid on and 10-12 minutes. Rice is done.

No matter what rice my husband cooks, he always produces Sticky rice. lol

and whoa to the person who grabs the salt shaker, unscrews it and dumps salt & rocks into the goulash!  Shaking action is the second function of the rice.   

I've seen plenty of rocks in some salt packages over the years and it didn't help with the moisture.  Some countries even have lids on the salt shakers.  Others serve a salty sauce instead for dipping:  soy, various fish sauces, etc..  Or serve salt in a tiny dish for "pinching."  

 

I don't know the reason for putting rice in salt shakers. It could be there as a desiccant, but I always assumed it was to keep the holes from clogging by breaking up clumps. (That's because I use rice as a mild abrasive, to clean out bud vases.)