Making a Yeast Starter for your Home Brew Beer

by Brad Smith on April 1, 2008 · 65 comments

The quality of your homebrew can be dramatically improved by making a yeast starter. Home brewers often toss a packet or vial of yeast into their beer without much thought to the quantity needed. Though modern liquid brewer’s yeast smack packs and vials are a huge improvement over older dry yeast packs, these packages do not contain enough yeast cells for optimal pitching. Underpitching results in slower startup, higher risk of infection, off flavors and sometimes incomplete fermentation.

How Much Yeast is Enough?

In general, lagers require a larger starter than ales. George Fix’s book “An Analysis of Brewing Techniques” recommends pitching rates of 0.75 mllion cells an ale and 1.5 million cells for lager. The number is measures in million of cells per milliliter per degree plato.

Converting to homebrew units, his ale figure translates to 4 billion cells per point of original gravity per 5 gallon batch (1.048 original gravity would be 48 points or 192 billion cells). For a 5 gallon homebrew, lets use the figure of 192 billion cells.

An average White Labs yeast vial contains around 100 billion cells of active yeast. Therefore without a starter, you would need two yeast vials to reach optimal pitching for our 5 gallon example. The large Wyeast activator packs contain around 100 billion cells as well, so again you would need two packs. The smaller smack packs contain only 15-18 billion active cells, so you would need 11 for the same 5 gallon batch. (Ref: MrMalty). Keep in mind you would need to double the above figures for a lager.

Fortunately, creating a starter is an excellent alternative to purchasing large quantities of yeast. Research varies, but a starter of 1 liter will yield approx 150 billion cells and a two liter starter will yield from 200-240 billion cells. So a 1.5-2 liter starter is sufficient for an average 5 gallon batch. For a 10 gallon batch, a 4 liter starter is appropriate (up to 400 billion cells yielded) but may require a two step starter (first a 1 liter starter, then transfer it to a 4 liter starter) if you are pitching less than 100 billion cells initially. (Ref: AHA Tech talk, 8/31/05)

Making the Starter

Creating a starter is very easy. You want to start 18-24 hours before your brewing session, so the yeast can reach an active state before pitching. If you are doing a two stage starter, allow 18-24 hours for each stage. I use a large pyrex flask, but a very clean pot is a suitable substitute of you can cool it quickly. Dry malt extract is easy to store and use in small quantities. To determine the amount to add, you can create a mini-recipe in BeerSmith that is the size of your starter and adjust for a target gravity of around 1.040. Alternately, use this rule of thumb: between 3.5 and 4 ounces of extract per liter (or quart) will give you a good starter.

Dissolve the dry malt extract, boil it for 10-15 minutes to make sure it is sterile, and then cool it quickly in an ice bath and transfer it to a sanitized container. Once it reaches room temperature, pitch your yeast and seal the container with an airlock to prevent contamination.

Allow the starter to ferment between 18 and 24 hours. Pitch the entire contents of the starter into your batch of beer to get an active, robust start. Pitching yeast at the proper rate will significantly reduce the lag before active fermentation begins, promote complete fermentation, reduce the risk of infection and improve the overall quality of your beer.

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{ 42 comments… read them below or add one }

Rep April 2, 2008 at 5:00 am

If I am washing and reusing yeast, how many ml’s would I pitch to the starter above?

TY – Nice article.

Brad Smith April 2, 2008 at 5:56 am

Rep – I usually pitch the whole thing into the starter and then pull a new sample for the next batch. You can reuse yeast for 5-6 generations before it is time to buy fresh yeast.

Jeff Louella April 13, 2008 at 12:08 pm

Would the use of a stir plate help increase the amount of yeast growth. Say instead of 150b with a 1L starter, you get 200b in the same starter?

Brad Smith April 13, 2008 at 12:20 pm

I would expect that a stir plate would increase the yeast growth. I found a reference that indicates that using a stir plat can increase the number of yeast cells by as much as 50% if the starter is also properly aerated.

Chad April 22, 2008 at 3:54 am

Jamil Zainasheff has a pitching rate calculator that makes it easy to figure out how big a starter you need.

There are variables for ales vs. lagers, use of stir plates vs. shaking the starter and reusing yeast slurry from previous brews. All in all a pretty handy tool.


thargrav November 30, 2009 at 4:48 pm

A stir plate will dramatically increase your starter volume because it keeps the yeast from settling out into a sediment in the bottom of the flask. This way all of your yeast can grow & multiply instead of just the yeast in the top layers of the sediment.

But the greatest benifit of pitching a starter is that you are pitching a active, growing yeast culture. And by doing so, you bypass the first two stages of yeast development and go straight inter fermentation. You air lock will be bubbling within an hour!

Darkshadow January 28, 2010 at 8:08 am

Could you please clarify the size of a starter for 10 Gallons? Do I make a 1 liter starter, then add it to a 4 liter starter for a 5 liter total, or do I add a 1 liter starter to a 3 liter starter for a 4 liter total?


Brad Smith January 29, 2010 at 12:22 am

Yes, I would recommend doing a step-up starter if you are going to do a 10 gallon batch from a single tube or pouch of yeast. You can roughly double the size of the starter for a 10 gallon batch over the sizes shown in this article to get your total starter volume.

Tour Golf Blog May 4, 2010 at 4:48 pm

Perfect. This is exactly what I needed to know. My recipe doesn’t have a DME, only LME and some grain, so I think I’ll need to pick up some DME for the starter. I’m shooting for an 8% ABV brew so I’m sure a starter is going to help get it there.

Felix July 27, 2010 at 3:28 pm

What are the downsides (if any) to using an unnecessarily robust yeast starter? I.E. using 3 liters on a lower gravity five gallon ale batch.

Brad Smith July 30, 2010 at 5:28 pm

Felix – Overpitching (too much yeast) is unfortunately not good for your beer either. If you overpitch, the yeast do not live through a complete yeast cycle and the beer will not ferment well and the yeast will have poor viability at the end of fermentation.

iamvav August 9, 2010 at 1:11 pm

Will overpitching result in a yeasty flavor in the finished beer?
I have a 10 gal batch lager that came out yeasty, and I am hoping the second 5 gal keg will have mellowed.

Joseph September 11, 2010 at 10:08 am

What size and type glass flask would you use to make a yeast starter for a 5-gallon batch?

Brad Smith September 12, 2010 at 6:19 am

I would probably start with a 2 liter flask – Brad

chris September 23, 2010 at 1:19 pm

what about the additional 2 liters of liquid you’re putting into the wort how do you account for that

Brad Smith September 23, 2010 at 6:04 pm

Chris – with a little planning you can easily account for the extra liquid in your brew – since it is added post boil, just reduce the amount of your “trub loss” by the size of your starter. — Brad

Felix February 26, 2011 at 12:35 am

Brad, great advice and great article, especially for any newbie to the yeaster starter area (like me). Thanks for the help and wisdom. I, and my friends who drink my homebrews, thoroughly enjoy it.

Brad Smith February 26, 2011 at 10:38 am

Thanks Felix,
I appreciate the kind comments – happy brewing!


Chris B March 24, 2011 at 10:39 am

If you are making a larger starter, say 1 gallon, do you have to do it in two steps? or can I simply use about a pound of DME and a gallon of water and pitch my yeast into that for a big starter?

Brad Smith March 25, 2011 at 8:24 am

If you are making a 1 gallon starter, I would say you do not need a two stage. Much larger than that, however, and you should probably consider it.


matt g May 22, 2011 at 12:25 pm


I have about 1 liter of clean yeast I’m planning on using. How much DME should I use to get it going in a starter?


Tom Perkins October 22, 2011 at 1:16 pm

I use molasses in a starter for bread, will that work for beer?

JIm December 1, 2011 at 8:05 am

Hello, I made a starter for the first time, just wondering if I pitched it right. I used 1 cup DME with 2 QTS. of water let it sit at 65 degrees for 48 hrs. It was pitched into a 5 gal Belgian Grand Cru Possible 8-9 abv. Thanks for any help.

Kleinabunen January 6, 2012 at 9:08 pm

I’ve followed these instructions and it’s now 12 hours later since I’ve initiaited this yeast starter, how do I know it is a success?

John January 28, 2012 at 8:28 am

I recently began making a yeast starter, and to minimize costs I used a packet of dry yeast rather than a liquid vial from White Labs or someone else. Everything seemed to work fine, but I am wondering now whether it would have been better to avoid using the dry yeast in favor of the White Labs vial. What do you think? Does it matter whether you start with one rather than the other?

Brad Smith January 29, 2012 at 1:54 pm

You generally don’t need a starter when working with dry packets – they only need be hydrated about 15-30 minutes before pitching. You need to make sure you have enough packets to achieve your pitch rate however. In the BeerSmith 2 yeast starter tool there is a calculator to help you determine the number of dry packets needed as well as the hydration needed.

Lewis March 1, 2012 at 4:57 pm

hi, firstly, thanks for the advice. 🙂

You mentioned that yeast can be reused about 5-6 times before having to buy fresh yeast – how do yeast producers harvest yeast in a way that is reproducable? Why can you only do it at home 5-6 times? Is this because it starts to taste of the wort it’s been growing in or something? If so, can you change the food to something like yeast food so it doesn’t take the taste of the malt? or perhaps washing it more regularly might enable you to use it more often?

Brad Smith March 5, 2012 at 11:36 pm

Yeast labs typically grow their yeast up from very small and well stored slants. They also have much higher sanitation standards across the entire process than an average homebrewer’s home or fridge. You can certainly use yeast over many times, but in a typical homebrew environment there tends to be some contamination with each generation.

Tony March 11, 2012 at 1:23 am

Making my first starter, I checked the BeerSmith yeast tab and it said I need a .5 liter starter to yield 285billion cells but your post above says a 1 liter starter will yield 150 billion cells. What am I missing?

Joe August 12, 2012 at 7:34 am

Should the starter be at fermentation temp. My thought is to make a true lager, I would have both the wort and started at 50 degrees and that after pitching it will go right into the dedicated refrigerator with temp. control device. There is one school of thought that pitching should be done at higher temps and brought down to 50 degrees.
Which method would you recommend

Chris Richer September 29, 2012 at 4:04 pm

Brad my question is this I have 1600 milliliters off work, washed in in 1 gallon jar. The yeast cake in the bottom of the jar is about 1 /2 to 3/4 thick . how much the yeast cake do I use to start.

Brad Smith September 29, 2012 at 6:45 pm

It depends on how fresh it is. If it is less than two weeks old you can probably use a cup or so of the good stuff. If it is much older than that you may want to pitch it into another starter as yeast slurry does not hold up well to age unless you go through the yeast washing process. There is an article here on yeast washing if you do a search here on the blog.

Dave Moore December 11, 2012 at 11:26 am

Just a comment that this is a really intelligently-done and useful service. (Based on my years as a Food Technologist and QA Manager for a dairy company with cheesemaking divisions). My son-in-law is asking for advice as a novice beer-maker and this is my go-to site now. Thanks.

Brad Smith December 11, 2012 at 1:01 pm

Thanks Dave – the kind comments are truly appreciated!

Jim December 14, 2012 at 10:53 am

I usually make 15gal of wort at a time and ferment in 3 5gal fementers pitching in a single yeast package for each fementer! If making a yeast starter for this, do I need to start with 1 package of yeast in 1 L of starter liquid(target gravity 1.040)for the 1st stage and then for the 2nd stage add more liquid (target gravity 1.040) to get the correct volume of starter? Do I need to add any more yeast packages?

joel March 8, 2013 at 11:53 am

Hi Brad!
I habe been brewing with allgrains for a while, and allways only used one pack of dry yeast for 20 liters. Now I will like to give it a go and to brew 30 liters. I will be ussing again just one pack of dry yeast, mutons 6grs, that is what i have. Where i am living it is extremelly hard to get beer yeast. So, the idea would be yo make a starter… hoy many litters will you recon i need to make a 32 or 32 liters batch (arround 7 gall)? also, to make the started I have no extract or anithing like that (you just cant get it over here). What will you recomend to use instead? I do have some yeast nutrient (got it a while ago when visiting NZ) and B1 vitamins. Well, how many liters of starter for a 7 gal batch? what to ad to this starter if i dont have extract or dry malt?

DAv_brew March 28, 2013 at 12:33 pm

how many time the stir plate should work? My friend think is all the night and more . Me, i am not sure and can’t find any information about it. I’m worry about, if it work too long a bad infection can go in …

DAv_brew April 5, 2013 at 9:30 am

Thank to beer geek nation for is review, he answer very well, minimum 6 hours to 24 hours and the yeast starter could stay on the stir plate all this time.

cml21 April 11, 2013 at 10:37 am

Hi Brad! Thanks for the article. I’ve used the process you outline above with great results.

I have a question about covering / air-locking your starter. It seems some people recommend bubblers, and other simply cover with aluminum foil. Is one used with stir plates and another without? Or, is this just two different philosophies? (It seems odd to me that we all fear contamination with 5 gallon batches, but some people only use foil to protect their starter.)

James June 21, 2013 at 6:39 am

Hi Brad

Thanks for the recent email on this topic. Do you have any comments re cell counts for bottle conditioning filtered / near sterile beer? I know it will depend on target CO2, and the beer profile will have an affect but I can’t find any information on it. It would be a really usefull tool in BeerSmith to work out the minimum repitch required based on the FG before bottling. (All this with the intention of minimum yeast deposits in the bottle).


Brad Smith July 5, 2013 at 11:47 am

I don’t have any actual cell counts. Certainly if I wanted minimum deposits I would probably keg it first and then bottle from the keg after it is carbonated and has settled. Also use of good finings for clarity and cold crashing the beer can help, though you need to be careful cold crashing before bottling as it can kill off your yeast needed for conditioning.

Fritz September 21, 2013 at 11:30 pm

Hi Brad. I usually make 10gallon batches at time. I haven’t washed my yeast before. How much water would you recommend washing my yeast cake with and in how big starter should i pitch this washed yeast? Thanks for a the great advice

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