11/28/2015

How many grams is a cup of flour?

A key milestone for my bread making was beginning to measure flour with a scale. It happened very shortly after I started, and I believe it was key to the early success that kept me baking. I still advise anyone attempting bread baking to use a scale for the best results.

Recently, I received another request from my mother for my bread recipe converted to volume measurement. Such requests had been made just about every time I went home. Instead of treating this one as a heretical request like those past, I decided to embrace it as a challenge. I asked myself if it would be possible to reach some degree of accuracy using measuring cups and spoons.    

My enlightenment was partly inspired by Alice Medrich’s recent book Flavor Flours. As with most good baking books, she provides mass measurements for all of the formula. She also describes how to measure flour by volume and provides a helpful appendix of volume measurements for the non-traditional flours used in the book. The key was providing a standard way to measure the flour in her discussion on measuring by volume.

Using Alice's description as a starting point, over a weekend, I conducted an experiment and collected some data. I decided to test the primary flours I use for baking bread. This had the advantage of also extending the information provided by Alice's appendix. The flours tested were:

  • Unbleached All-Purpose Wheat Flour (Gold Medal)
  • Unbleached Bread Wheat Flour (Gold Medal)
  • Whole Wheat Flour (King Arthur)
  • Medium Rye Flour (Grocery Store Bulk )
  • White Rye Flour (Grocery Store Bulk)
  • Whole Spelt Flour (Arrowhead Mills)
  • Semolina Flour (Caputo)

I experimented with three different techniques to measure the flour. The different techniques demonstrated both the strong dependence on measuring technique, and the variability that occurs when measuring flour by volume. The three measuring techniques were as follows:

  • The first technique I call the “tamped” method. This is the “take the measuring cup and just scoop the flour out of the container” method. In most cases, flour started out rather compacted in the container and got tamped into the measuring cup by the side of the container on the way out. The only refinement in this method was a kitchen knife was used to strike the excess flour off the top of the measuring cup.
  • The second technique I call the “fluffed” method. In this case, a kitchen knife was used to aerate or fluff the flour in the container before the measuring cup was carefully used to scoop flour from the center of the container. Care was taken not to compact the flour on the way out. As with the tamped method, the kitchen knife was used to strike any excess flour off the top of the measuring cup to maintain uniformity.
  • The last technique tested was to spoon flour from the container into the measuring cup until there was a heaping mound. As with the others, a kitchen knife was used to strike the excess flour off to get a uniform measure. For this last technique, I selected the extremely original name of “spooned” method.   

For the three standard wheat flours and the two rye flours, I collected data for each of the three techniques. I don’t keep large amounts of spelt and semolina flour around so I only collected data for the fluffed and spooned techniques. In both cases, I didn’t feel I had a large enough volume to consistently collect data using the tamped technique.

To collect measurements for a full-cup of flour, I measured out four cups of flour and recorded the mass using a digital kitchen scale after each cup. After measuring four cups, I returned the flour to the storage container and repeated the procedure two more times for a total of three trials. After some subtraction, this resulted in twelve measurement samples for each experimental run.

When you combine the 7 flours with the 3 measuring techniques and 3 trials for each, you end up with a total of 57 experimental trials and 228 individual data points. A Google Docs spreadsheet was used to summarize the data and compute some statistics. With 12 measurements for each combination of flour and technique, the standard deviation for most of the combinations was in the 2-3 gram range. The tamped technique showed the most variability; this is an additional finding I will talk more about in the closing. The table below gives the mass in grams for 1 standard US cup (240 ml) of flour using each of the three measuring techniques.  

Mass in Grams per US Cup
Tamped
Fluffed
Spooned
AP Flour
148
140
135
Bread Flour
150
143
135
Whole Wheat
155
143
133
White Rye
130
120
112
Med Rye
125
119
112
Whole Spelt

149
138
Semolina

170
155

I also wanted to see how reliable the measurements would be when using a half-cup and a quarter-cup measure. I did experimental trials with bread flour as before, except I switched the size of the measuring cup from a full-cup to a half-cup and then a quarter-cup. The results were compared to what would be predicted by just taking the corresponding fraction from the mass for a full-cup. With surprising consistency, a lose of about 6% is observed as you move from one measuring cup size down to the next. For instance, a half-cup (fluffed technique) of flour measured out to be 67 grams when it would have been predicted to be 71 grams when you take the measurement for the full-cup (143 grams). For simplicity, 6% was selected as a uniform correction factor to generate the following tables for half-cup and quarter-cup measurements.   

Mass in Grams per US Half-Cup
Tamped
Fluffed
Spooned
AP Flour
69
66
64
Bread Flour
70
67
63
Whole Wheat
73
67
63
White Rye
61
56
53
Med Rye
59
56
52
Whole Spelt

70
65
Semolina

80
73


Mass in Grams per US Quarter-Cup
Tamped
Fluffed
Spooned
AP Flour
33
31
30
Bread Flour
33
31
30
Whole Wheat
34
32
29
White Rye
29
26
25
Med Rye
27
26
25
Whole Spelt

33
30
Semolina

37
34

For completeness I provide the following table for tablespoons, however it is just a guide. By the time you get down to a tablespoon fraction, the error of the experimental measurements starts to be on the same scale as the amount of flour you are measuring. You would need to actually collect experimental data using tablespoon measures to resolve this. For the same reason, I only present the fluffed technique.

Mass in Grams per US Tablespoon
Tamped
Fluffed
Spooned
AP Flour

8

Bread Flour

8

Whole Wheat

8

White Rye

7

Med Rye

7

Whole Spelt

8

Semolina

9


One additional outcome is a recommendation on measuring technique. As hinted before, the tamped technique of measurement had the most variability in the experimental data. This stands to reason given the nature of the food stuff that is being measured. I would recommend sticking to either the fluffed or spooned methods. This is consistent with the advice given by Alice, and I have found the same guidance in other cookbooks as well.    

The goal of this exercise was to come up with a reasonably accurate way to measure flour using traditional volume measuring cups. The tables presented accomplish that goal, and give a series of conversions that allow someone to go from grams to US cups, half-cups and quarter-cups. Happy baking.  

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