How Big Should My Yeast Starter Be? Yeast Starter Size

May 4,2010 by 23 Comments

Note: This video is a precursor to my video on how to make a yeast starter, which goes into the “why” and the “how” of starters. Check out that one for a step-by-step.

Yeast starters are a great way to improve the quality of your homebrewed beer. While it is almost always a good idea to make a starter, the size of the starter is very important in order to achieve the proper pitching rate for your beer. Starter size is based on a handful on conditions:

  • Ale vs. Lager
  • Yeast viability
  • Batch size
  • Original gravity
  • Aeration (Oxygen)

The pitching rate calculator on Mr. Malty is a simple and useful tool that will allow you to determine the correct yeast starter size.

You’ll notice in the video that the calculator can spit out some really high numbers for the starter size. I know I don’t have a 6 liter flask lying around, so something of that size is out of the question (for now). You might find yourself in the same situation. Instead of skipping the starter altogether, just make the biggest one you can with the equipment you have (flask, growler, jug, etc.). You’ll still activate the yeast and get them ready for fermentation.

Do you vary the size of your starter? Have you used Mr. Malty before?

About Billy Broas

He is the founder of The Homebrew Academy, a BJCP beer judge, and the homebrewing expert on the Rocky Mountain PBS television show Colorado Brews. He lives in the fine beer town of Denver, Colorado.

23 responses to “How Big Should My Yeast Starter Be? Yeast Starter Size”

  1. Ted says:

    The bar at the bottom of the calculator labeled growth factor is preset to 3, what is 3 refering to if you pitch the number calculated? If the number refers to how fast it grows how did they decide on 3… 3 what? lol.

    anyways, thanks.

    great site

  2. Billy Broas says:

    @Ted Yea the growth factor bar is pretty confusing. Here is Jamil’s explanation of it, which still isn’t too clear:

    While I’m not entirely sure what the GF means, I know that the bar is best used to suit your brewing needs. So if you want to use less yeast packs and have a bigger starter slide it to the right. If you want to use more packs and have a smaller starter slide it left. Seems like it would make more sense to let you type in how many yeast packs you want to use and it would tell you how big your starter needs to be. Unless I really don’t have a clue of how this thing works.

  3. Thile says:

    I did a yeast starter for the first batch, but didn’t really know what I was doing – followed the instructions on the starter kit. Mr. Malty was confusing to me but now I think I have at least an idea of how to use it.

    So thanks for the video! It looks like for one of our three kits I’ll have to get some yeast in prior to brew day!

  4. Nels says:

    I’m planning on brewing a lager soon. I’ve looked on the Palmer book for where it describes pitching rates for pagers and from that I determined I need about a 3 quart starter. But the pitching rates for lagers on Mr Malty is WAY higher! What’s with the discrepancy?


    • Billy Broas says:

      Hey Nels. I checked out my How to Brew book and his numbers really look low. For a 1.055 lager he recommends 170 billion cells, whereas Mr. Malty recommends 384 billion. That’s a pretty big discrepancy, and I haven’t heard anyone raise the issue before, but I would go with the Mr. Malty numbers. 170 seems way too low for a lager.

      • Nels says:

        Yeah, it’s true, the numbers are pretty different. Argh! The lazy part of me would rather go with the lower numbers, but this is my first lager so I feel like the stakes are pretty high. I’m going to try to find Palmer’s email address or something. It’d be nice to hear from him on this subject…


        • Billy Broas says:

          That is frustrating. I would also be tempted to do Palmer’s numbers but I’m sure you’re beer will thank you if you take Mr. Malty’s advice. If you hear from him, let me know.

  5. Brian says:


    I have a Wyeast Activator pack #1968, that I bought from a local home brew supplier, but failed to check the date. I mixed up my 1L starter and through it on my stir plate and while cleaning up my mess, noticed it was MFG’d in July of 2009 :-/

    Not wanting to waste my starter, I went ahead and just let it ride…figured it would eventually activate and start showing signs. However, it’s been 36 hours and I can’t see any visible activity in the starter yet. Nothing floating/spinning around in side, but the brown wort. So…I am wondering…is it worth it to let this ride and see if it will activate and eventually be usable, or should I just trash it and start with fresher yeast?

    I brought the package back up to the supplier who let me swap it out for another…It’s not as old, but it was MFG’d in March of 2010, so a bit over a year ago. I smacked it, and shook it up good last night and as of this morning…no swelling in the package yet..but I am hoping it will swell given a bit of time…say a couple days. I’ve read of stories where wyeast refrigerated for several years eventually activated so am trying to remain optimistic. If this other pack does activate (swells) before any signs of activity in the starter on the stir plate. Would you recommend pitching it into that starter or starting all over with a fresh batch?

    Thanks in advance for any thoughts/suggestions on the matter.


  6. Billy Broas says:

    Hey Brian,

    Your local homebrew supplier shouldn’t be selling you yeast that is that old. The shelf life for Wyeast is 6 months. If it were 7 or 8 I could maybe understand but over a year is unacceptable. I just checked a Wyeast package I bought yesterday and it was manufactured 1 month ago. If I were you I would get a refund and get your yeast elsewhere.

    This is why we make starters. If you had added that dead yeast to your beer you’d be in a much worse spot than you are now.

    Also check the Wyeast FAQ – they have good info there.

    • Brian says:

      Well, the plot thickens! For starters…my math was off…the starter I prepared with the 22 month old yeast is now just 48 hours old, not 36. When I got home from work, I now notice some activity. The funnel of the “whirlpool” formed by the stir plate, now is white and I can see some scant amount of floating white stuff spiraling around too. Soo…not sure what to do at this point. Looks like it is activating after all. So…should I let this go another 24 hours and then chill it to settle out any yeast and decant off and prepare another starter with these newly activated yeast?

      That brings me to another question. With a 1 liter starter prepared from 3/4 cups of DME (100 g), what sort of increase in yeast should you expect…or is it just capable of a FLAT # of cells? Not sure what to make of this starter and ITS viability. Will it be potent enough on its own to pitch (doesn’t seem likely to me), or should I do like I said above…decant and prepare a fresh starter from these newly activated and replenished yeast?

      • Billy Broas says:

        The 1L starter you made was probably too small given how old the yeast was. Did you plug its date into Mr. Malty? The starter size will increase the older the yeast is. You’ll have to use that number of yeast cells to figure out where to go from there. If it gets you to about the same number as a fresh pack, then you can do like you said and make a fresh starter. I would still find a fresh pack though since I wouldn’t want all of those dead yeast cells in my beer. At that age you have to worry about off-flavors.

  7. Malthead says:

    Billy, I’ve washed a yeast based on your video and have 4 X 1 Pint mason jars. I now want to make a starter with the washed yeast. What’s the recommended amount of washed yeast to use as a starter? Thanks.

  8. Prantick says:

    Hi, I am new in brewing thing. Just wondering about the Mr Malty pitching rate calculator. If I use dry yeast there is no calculation for starter volume and re pitching info. Most of the website I found the info for small batch. what should be the guideline for 1000lit Ale batch of OG 1.070, and pitching rate 1.5mil cells/ml/plato . I can easily calculate the total number of cells needed for final pitching but what should be the starter volume for two stage propagation with a minimum number of dry yeast packs for example if I use wyeast large pack. Also how large starter volume will not affect my final alcohol%. as I have to use low gravity for the starter then if I use large volume for starter will it not dilute the whole batch reduce the final intended alcohol% . Please give me some guide line how to manage the starter volume for the yeast propagation. Do I just need to prep roughly and decide with cell counting and cell viability of the starter for final pitching?

  9. Sean says:

    I’d like to embed it in another site, if that’d be ok… any chance it’s on Youtube or Vimeo (or somewhere with an embed HTML code)?

  10. Franz says:

    This is a great resource! I got a bit behind with my brewing schedule, and have a Wyeast Oktoberfest smack pack from August 2013. Fortunately, I didn’t just make my normal starter to send the wort on its way. I’m going to check out your video on stepping up yeast starters so I can see if I can squeak by with the one smack pack I have. (Closest home brew shop’s about an hour away … ).

  11. Andy says:

    So, with the 1.065 example, does that mean I need almost 3 liters of slurry or does 3 liters include the original starter wort volume? Either way, this seems huge. Its over 12.5 cups of liquid right? Am I missing something?

    • Billy Broas says:

      Hey Andy, it’s 3 liters of wort not yeast slurry. Yes it’s a lot but keep in mind that’s with no oxygen. With a stir plate that comes down to about 1 liter.

      • Andy says:

        That makes sense. I just got a great deal on a stir plate (, so I’ll be trying your starter recipe with that soon!

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