Grain, Spawn & Bulk Mushroom Substrate Calculator for Monotubs, Buckets & Polytube Logs.

Welcome to! 

We help you save money & help you calculate how much of each material you need for your Monotub! 

Should You Buy or Make Sterilized Grain?

Including shipping anywhere in the USA, you can get sterilized grain for $2.33 per pound, so if it costs you more to make then you are better off buying it. 
You can buy it here: Sterilized Hydrated Grain - 3 pound bags with injection port 


Sterilizing grain in a pressure cooker can be smelly, noisy, time consuming and potentially dangerous.  Pressure cookers are expensive, homemade filter jars may not properly keep out contaminants, and using professional mycobags requires a pricey impulse heat sealer. Include these factors into your decision to make or buy grain. 


1. Cost, per pound, of unprocessed grain: $ per pound
2. Value of your time: $ per hour
3. How many pounds of hydrated can you sterilize all at once?: pounds
4. Amount of Labor, in hours required to get, hydrate, bag, sterilize, and cool grain: hours
5. How much does 1 pound of grain weight once hydrated? pounds
6. How much do all of the consumables (filters,bags, injection ports, etc) cost you? $

If you're using the Vespco Bags of Sterilized Grain, know that 1 bag is equal to 3 jars that are 3/4 full.

Calculate Amount of Spawn & Bulk Substrate Needed for Your MonoTub!

Required Inputs for Calculation:

(green fields are required)

Container & Substrate Size Information:

Container Radius:inches

Desired Substrate Depth:inches

Desired Spawn Ratio:


Ratio of 1-to-

How Full Are Your Spawn Jars?




Substrate Will Be Made of What % of the Following Ingredients:

(Gypsum will not be added to the running total as it is considered a "non-volume adding" ingredient)

Coco Coir:Percent


Coffee Grounds:Percent


Hay or Straw:Percent


Horse Manure:Percent

Cow Manure:Percent

Chicken Manure:Percent

Worm Castings:Percent


Current Total: 0 Percent

Your Results:

(after you've filled in the input fields click the calculate button on the left)

Total Substrate Volume In:







The Final Mixed Substrate Will be

0% Spawn & 0% Bulk Ingredients

You'll Need a Total of 0 3/4ths Full Quart Jars of Spawn & 0 Quarts of Pasteurized Bulk Substrate

Volume Required of Each Individual Substrate Component In:



Coco Coir:


Coffee Grounds:


Hay or Straw:


Horse Manure:

Cow Manure:

Chicken Manure:

Worm Castings:




























Please Select Your Bulk Substrate Container Shape:

(on the following page, you can mouseover any red question mark to clarify something you don't understand...try it:)

Break Even Analysis: 

Your Cost to Prepare One Pound of Sterilized Grain (Results of first calculator) Cost of Pressure Cooker Cost of Impulse Sealer

Laminar Flowhood Calculator: What Blower do you need for your filters?
(Underdevelopment, not working yet!)

I have filters, what blower do I need?

HEPA Filter
HEPA Filter Hieght:
HEPA Filter Lenght:
HEPA Filter Resistence:

Does it have a prefilter? Yes/No
If no: all equal 0
Prefilter Height:
Prefilter Length: 
Prefilter Resistence:
Prefilter resistence + HEPA Filter Resistence = Total resistence. 
Desired feet per minute: (Recommended at least 150 fpm, but 100 fpm works).
You need a blower that equals:   CFM at total resistence. 

((Width x height)/144) x feet per minute = Needed CFM of blower
Needed CFM of blower at resistence:
100 x resistance of filter/test flow of filter

I have a blower, what filter(s) do I need?
Due to variations in resistance in filters, it gives us two variables (s


Our Recommendations

1. We believe the 23 Quart Presto Pressure Cooker is the best for this purpose: It can fit 10 quart jars in it, or up to 24 pounds of grain in spawn bags. It costs $100 or less and is easy to move around. The best place to get it is either or Replacement parts, such as the rubber seal, weights, or gasket are often available at Ace Hardware. 

2. The All American Pressure Cookers that are larger are significantly more expensive and harder to move around by yourself. While they are more reliable, replacing a rubber gasket on the Presto is cheap and easy. You can buy four 23 quart pressure cookers for less than the price of a single 41 quart All American. This results in more than double the cooking volume, and it allows you to pressure cook different things for different lengths of time simultaneously, unlike owning a single large pressure cooker. If you do agar work, liquid cultures, grain, bulk substrate, supplemented sawdust blocks - this feature comes in handy. 

3. Consider you can always sell your pressure cooker and impulse sealer later  to reclaim some of the initial investment. These calculations don't include the money you might make back on selling the used items, or the effort required to sell a large pressure cooker. 

4. We suggest using filter patch bags that are 0.2 micron and not 0.5 or 5.0 micron for spawn. Trichoderma spores are 0.3 micron in size and so the 0.5 and 5.0 micron bags can contaminate, while the 0.2 micron cannot unless the filter is faulty (not common). 

5. If you can, we highly recommend using a double impulse sealer that is wider than 2 mm. The most common impulse sealer is 2 mm wide and a single sealer; this causes significant difficulty because the spawn bags are gusseted and often 3 mils thick. This results in 4 layers of 3 mil thick plastic in some areas where it is folded, and 2 layers thick in other areas. If the single sealer is used, you have to get one side hot enough to fuse all 4 layers of plastic together; this inevitably gets the 2 layers of plastic too hot and it will melt so much that it can leak. If you do not fuse all four layers, the interface between the two layers of plastic and the four layers of plastic will often have a small leak which can let in airborne spores. Doesn't always happen, and it won't always contaminate; but it is annoying as hell. We purchased a double sealer that is 10 mm wide so we don't deal with the issue, but it set us back $205 dollars.  

6. We have better luck with spawn bags that are 3x4x18 in size as opposed to the 8x5x18 bags. The larger bags are great if you are doing it on a serious scale but if you are growing mushrooms inside your house, the 3x4x18 are perfect. They hold 3-4 pounds of grain which is enough for most monotubs and if your growing oyster mushrooms a single bag can innoculate nearly 100 pounds of pasturized straw.

7. When it comes to grain we think it is the best to go with grain used for planting or animal feed. Organic grain is a gimmick but it allows you to sell your mushrooms as organic later on.  Grain used for human consumption is significantly more expensive than kind used for feed or seed. . Each grain has it's pros and cons, but the main thing you'll want to consider is that not all grain is cheaply available year round. Rye tends to become unavailable during certain months, while Sorghum (Milo) and millet are available year round. Smaller grain is good because it results in more innoculating points per pound and per cost, but it tends to have lower nitrogen levels.

To reiterate, We'd buy the 23 Quart Presto Pressure Cooker and something like an 8 inch, double sealer that is 5mm or wider. This will set you back nearly $150, but if you are making enough spawn, and you can make it cheap enough - it will be well worth it. The best spawn for several reasons is a 75% Sorghum, 25% Millet mixture. 

Useful Resources:

Easiest way to prepare grain:

Add 260 grams of Sorghum to a quart jar with 200mls of water. Put in the pressure cooker for 2 hours. No need to soak or prepare before hand, but you will need to shake it while it is still hot/warm after cooking it. This will produce 1 pound of sterilized grain per quart jar. 250 grams of Sorghum is about equal in volume to 200mls of water, it doesn't have to be perfect. Wild birdseed can be used in place of sorghum and it is available at most stores. 

Thoughts for Consideration

Monotub Tips & Tricks:


Q: When to harvest?
A: Right before the viel breaks. The viel is a thin membrane under the mushroom cap that covers the gills. It breaks off before spores are released. 

Q: When should I put into fruiting conditions?
When the substrate is fully colonized. This takes about 2-3 weeks if everything is going well. 

3. What is field capacity  & how do I determine if my substrate is at field capacity?

Q:What is the best ratio of spawn to bulk substrate?
A: This depends on many factors. Higher spawn will colonize quicker and provide more neutrients. This results in higher yields and a lower risk of contamination. The cost and work involved goes up as you need more grain which is more expensive than coco coir. You can also run into reduced moisture content which can hurt yields. 

Q: Can I reuse a tub that housed contaminated substrate?"
A: Yes you can, just clean it out with soap and water. If you're extra paranoid, you can use bleach or hydrogen peroxide. 

Q: Why do my mushrooms keep aborting? 
A: This likely means that you need to increase the humidity as dry air can cause the mushrooms to abort. 

Q: My mushrooms are tall and skinny
A: They need more fresh air. Being tall and skinny is a sign of elevated CO2 levels. 

Q: There's green or other unwanted mold growing, is all hope lost?
A: It will probably be okay, but yields will be lower. Next time try adding more spawn, a casing layer, and ensuring that your bulk substrate is properly pasturized. Also make sure the lid is on well. Green mold is also a sign of not enough FEA. It seems to do better in high CO2, high humidity enviorments. 

Q: Should I mist the Monotub?
A: If done properly, you won't need too - but if it seems to be drying out or is not humid enough, yes you should then mist it. 

Q: Should I mist the substrate or just the walls & lid?
A: This is debated so it likely doesn't matter too much. So long as you are only misting when needed, misting the substrate and the walls shouldn't be a problem. 

Q: Can I use crumbled colonized BRF cakes for spawn?
A: Yes you can! This is a good method to by pass the need to pressure cook as PF-Tek substrate can be processed by steaming them for at least 90 minutes in a boiler. 

Q:  When should I mix or shake my grain?
A: Anywhere from 1/4 to 1/2 colonized. This isn't needed but it will greatly speed up colonization rates. 

Q: What temperature should I keep my colonizing substrates at?
A: Just use room temperature. 

Q: Do they need to be in the dark or do they need light?
A: They do not need light except for a small amount to induce pinning. 

Q: How long does it take to grow mushrooms?
A: Approximately 1 to 1.5 months if you are stating from scratch.
2-5 days to get spores or cultures in the mail, 2-5 days for the spores to germinate, 5 to 10 days for the grain to colonize, 7 to 15 days for the bulk substrate to colonize and be ready for fruiting conditions, 5-10 days for substrate to grow mushrooms that are ready for harvest. 

Q: How much do dry mushrooms weight compared to fresh mushrooms?
A: 10% - When a mushroom dries out they lose 90% of their weight as they are mostly water. 100 grams of fresh mushrooms will weight only 10 grams dried. Though it varies a bit depending on species, strain, harvest time, substrate, and envirement.

Q: What is the best way to dry mushrooms?
A: A food dehydrator. 

Q: I don't have a food dryer, how can I dry my mushrooms?
A: Place them on a tray inside the oven on low with the oven door open. This will allow the hot convecting air to dry them out. 

Q: What is the best way to preserve my mushrooms?
A: Make sure they are cracker dry, put them in an airtight container with some dehydrated epsom salt (Magnesium sulfate), and put inside the freezer. They will last for years unaffected. 

Q: What kind of yield should I expect?
A: It depends on many things but the weight of the fresh mushrooms should be 100% to 150% the weight of the dried substrate. If you use our 3 lbs sterilized grain and a 1:3 ratio of coco coir, straw, vermiculite, and gypsum you can expect approximately 130 to 200 grams of dried mushrooms under good conditions and using a good high producing strain when fruiting until the substrate is spent.

Q: Is a SGFC or mono tub necessary only if you're not going to fan often? Would a SGFC have a problem retaining humidity?

Q: What is the no holes tek? Is it better than the monotub?

Q: How do I know if my grain is contaminated?

Q: The mycelium isn't colonizing the entire substrate, why?

Q: What is the best size of Monotub?

Q: Can I mix two different strains of mushrooms in the same substrate?


Stay Safe & Happy 'shroomin!

If you need any guidence, hit me up and I will help you out as much as I can. 
Contact me:
Message me on Ves


Information & Community Resources:

Mycology Supplies:

Spore Syringes & Spore Prints

Acronyms used in Mycology:

50/50  = 50% vermiculite/50% peat moss
50/50+ = 50/50 with gypsum, lime, or oyster shell added to buffer the pH
BE     = Biological Efficiency
BRF    = Brown Rice Flour
BTW    = By The Way
CEV    = Closed Eye Visuals
coir   = coco coir; coconut fiber; coconut "hair"
DDI    = Double distilled De-Ionized water
DI     = De-Ionized water
DT     = Double Tub
EtOH   = Ethanol
FAE    = Fresh Air Exchange
FC     = Fruiting Chamber
FH     = Flow Hood
FOAF   = Friend Of A Friend
G2G    = Grain to Grain [transfer]
GB     = Glove Box
HEPA   = High Efficiency Particulate Arrestor
HW     = Honey Water
IME    = In My Experience
IMHO   = In My Humble Opinion
IMO    = In My Opinion
IPA    = IsoPropyl Alcohol
KISS   = Keep It Simple Stupid
LC     = Liquid Culture
LS     = Lab Strain
MC     = MonoCulture or Mushroom Community
MMGG   = Magic Mushroom Growers Guide
MT     = Mono Tub
Martha = A shelf sealed in a zippered plastic cover (Is that a good description?)
MeOH   = Methanol
OEV    = Open Eye Visuals
OMC    = Online Mushroom Community
OTOH   = On The Other Hand
PC     = Pressure Cooker
PF     = Psilocybe Fanaticus
PMP    = Poor Man's Pod
RH     = Relative Humidity
RTF    = Read The FAQ
RTFM   = Read The Fucking Manual
SBI    = Single Basidiospore Isolate
SWIM   = Someone Who Isn't Me
TC     = Take Care
TiT    = Tub in Tub
VOC    = Volitile Organic Chemical
WBS    = Wild Bird Seed
WT     = Wild Type
WTF    = What The Fuck
YMMV   = Your Mileage May Vary
aq.    = aqueous (water based)
dH2O   = distilled H2O (water)
inoc   = inoculate
karo   = A brand of light corn syrup (dextrose)
myc    = mycelium
noc    = inoculate
nock   = inoculate
pin    = primordia, the beginning of a mushroom fruit body
ppt.   = precipitate
soln   = solution
topia  = mycotopia, a shroomery knockoff created to sell Hippie3's products.
v/v    = volume/volume
verm   = vermiculite
w/v    = weight/volume