The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Density of Instant Dry Yeast

onymous's picture

Density of Instant Dry Yeast

I'm baking my way through Jeffrey Hamelman's 'Bread'. Because just my wife and I do the eating, I'm simply dividing the Metric Column in the recipes by 30 to obtain approximately one loaf -- the home column is not in metric and yields too many loaves for us.

Everything works out hunky-dory except for the Yeast amounts. My scale only has a resolution of 1 gram and I therefore have to convert to volume (in tsp).

For instance, Pain Rustique, needs 140g FRESH yeast. Divide by 30: 4.67g FRESH Yeast needed. Convert to INSTANT yeast: 4.67 * .33 = 1.54g INSTANT Yeast needed.

I now use a density of .6 to convert this to a millilter measure: 1.54g / .6 = 2.57ml instant yeast.

This, in teaspoons, is about .5 teaspoon.

(Of course, I combine all these factors into a single factor ( 1 / 30 * .33 / .6 / 4.93 = 0.0037) that I use to multiply the original fresh yeast amount)

BUT, I'm uncomfortable by the density figure of .6 that I'm using. Today, I saw a reference claiming it was just .5 but I can't find that URL again.

Also, while I'm about it, is the density of INSTANT and ACTIVE DRY yeasts more or less the same?

I hope I'm not cluttering up the forum with a question that's been answered multiple times. Thanks.


Emelye's picture

I use a density of instant yeast of .1 oz, or 3.4 g per teaspoon in the spreadsheets I've been working on (percentage forumla conversion & cost).  So far that has worked out for me pretty well.

I'm not sure where I got that from, however.  I think it was derived from the formulas in Reinhart's Bread Baker's Apprentice, or maybe another source, that gave yeast quantities in both teaspoons and grams.  I'll be looking forward to hearing some more from the more experienced people in the forum.


wayne on FLUKE's picture
wayne on FLUKE

According to:

"One 1/4 oz. packet (7g) or 2+1/4 tsp"

This would mean 1 tsp would weigh 3.1 grams or 1/2 tsp would be 1.55 grams.

Since you caclulated 1.54 grams I would say you are right on with your method.

As far as Active Dry vs Instant I think the density is very close. What is different is the size of the granules and the percentage of living/dead yeast with Instant being finer and having less dead "guys".


Chuck's picture

...scale only has a resolution of 1 gram and I therefore have to convert to volume...

Yep, any scale with a decent capacity only has one gram resolution and so can't be used to measure the small stuff, while any scale with a finer tenth of a gram resolution only has a small capacity and so can't be used for things like flour. The solution? two scales.

To find the small scales that work great for things like yeast and salt, search (for example on Amazon:-) for "digital pocket scale". I've personally had this one for well over a year now; I've had no problems (I did have to replace the batteries once though) and love using it. It allowed me to completely get rid of measuring spoons and measure all my ingredients by weight.

These things are real cheap - less than $10 total (even with shipping) with just a little shopping care.


(Do note that sometimes the same scale is available from more than one reseller, sometimes at quite different prices. Skip the higher priced ones. Also, note that many of them are shipped with an almost-invisible cellophane cover sealing each battery to prevent any possibility of discharge during shipping. You of course have to remove the cellophane before the scale will work.)

[Edit next day:] Also a word on "calibration"... I have never "calibrated" my scale. It was already calibrated when it arrived, and it hasn't drifted. (This is partly a holdover from my previous life as a software supporter, but I think there's a lot of wisdom in the proverb even if its source is a bit suspect; it says: "If it ain't broke, don't fix it.") Unnecessary calibration offers you an excellent opportunity to shoot yourself in the foot by making a perfectly good scale read incorrectly. (The computer lingo for this is "bricking".)

Also note that these inexpensive scales are very fussy about exactly how much calibration weight they require. For example the referenced scale can be calibrated only with a 500 gram weight, not with anything less nor more. (The packaging of the scale with a 100 gram calibration weight by one of the resellers is complete nonsense - owners who have purchased that and then called the manufacturer for help have elicited a lot of laughter:-)

MichaelH's picture

One of my hobbies is shooting firearms, for which I load my own ammunition. Subsequently I have a standard reloading scale which is used to measure the weight of the gunpowder for each cartridge.

The accuracy of the scale is .1 grain. 15.5 grains is equal to 1 gram, which makes measuring very small amounts an easy task.


onymous's picture

for the replies. I can now proceed without that nagging thought that I may have the incorrect amount of yeast.

I've also ordered the pocket scale. One of the customer comments on the scale was a suggestion to just use pennies (they weight 2.5 grams each) to calibrate one's scale. One caution: only pennies from 1983 onwards can be safely assumed to weigh 2.5 grams: earlier ones were heavier. Nickels alwaays weigh 5 grams.

Chuck's picture

oops, wrong date, posting removed by author

Emelye's picture

Does rounding up or down to the nearest gram for yeast really make that much of a difference?  The only time I really use small, less than 1 g, amounts of yeast is when making a poolish.  For that formula I use 1/8 tsp instant yeast.  Having made this poolish a number of times now, using volume measurements for the yeast, Ive seen no evidence that I can sense of ay varability in the yeast's performance.

Just wonderon'  :)


Chuck's picture

I think it depends on batch size.

I tend to make very small batches: just one medium-small loaf, typical flour weight 400 grams. My experience is with these small batches rounding to the nearest gram is not okay (especially for salt).

subfuscpersona's picture

I calculated the density to weight of IDY by weighing one level teaspoon IDY on an Ohaus Harvard trip balance scale. (This scale is used in labs and is accurate to 1/10 of a gram)

I weighed 1 level tsp IDY 20 times, recorded the weight of each trial and then averaged the weights. The average was 3 grams . There was very little variance.

My result is quite close to others' mathematical calculations of slightly over 3 grams for one tsp of IDY. (Ain't math grand!)

=== PS === Bought the Ohaus scale years ago primarily for making small batches of spice blends (aka Indian "garam masala").