Headspace For Canning – Canning Safety Series

by Suzan Ferreira
Headspace For Canning featured image showing 3 empty mason jars with headspace measuring tool placed in largest one

Canning headspace is a term canners of all levels will want to become very familiar with, understand its importance, and put into practice.


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When it comes to canning & preserving your own food, safety is paramount. It’s my goal in this canning safety series to help guide you (think beginner here) or remind you (yup, I need reminding all the time) of how you can put up your families food safely and without issue.


Understanding why it’s important to follow safe canning guidelines and practices is the first step in, well, creating safe food to eat. Although there are many safety guidelines which need to be met in order to have this happen, the biggest concern of not canning safely is botulism.

Botulism is real people. It’s not something that only happened in the 1600’s. It can and does happen, although in rare instances, in present time.


According to a quick Google search, the definition of botulism is as follows:

“food poisoning caused by a bacterium (botulinum) growing on improperly sterilized canned meats and other preserved foods”

Oxford languages

Botulism, according to the CDC, “is a rare but potentially deadly illness caused by a poison most commonly produced by a germ called Clostridium botulinum. The germ is found in soil and can survive, grow, and produce a toxin in certain conditions, such as when food is improperly canned. The toxin can affect your nerves, paralyze you, and even kill you.”

Definitely not something to fool around with. Any even scarier? Botulism is literally undetectable to the average person. It cannot be seen, smelled, or tasted even in small amounts. It’s deadly and needs to be taken seriously.

Organically Rooted Garden Group 728x90 banner image showing hand holding garlic with roots and name of facebook group

Other canning safety guidelines will be gone over in-depth in upcoming posts. Think equipment, recipes (always use safe canning recipes only & leave your Grandmother’s recipe alone), sterilization practices and more.

Today, we focus on headspace.


By definition, canning headspace is the empty space at the top of the jar which is left between the food or liquid you’ve placed in the jar and the top rim of the jar where the lid is placed. It’s this empty space that is paramount in creating an end product that is shelf-stable and safe to eat.


Why is this “empty” space so important? Largely to create a safe seal. To ensure that the jar is sealed properly will reduce risk of unwanted bacteria entering the product.

Headspace For Canning pin for Pinterest showing featured image of 3 empty mason jars with headspace measurement tool in quart size jar

According to my favorite source for all things regarding safe canning practices, the National Center For Home Food Preservation, it’s important to have the right amount of headspace when canning for the following reasons.

“If too little headspace is allowed the food may expand and bubble out when air is being forced out from under the lid during processing. The bubbling food may leave a deposit on the rim of the jar or the seal of the lid and prevent the jar from sealing properly. If too much headspace is allowed, the food at the top is likely to discolor. Also, the jar may not seal properly because there will not be enough processing time to drive all the air out of the jar.”


They even go so far as to recommend that no food should be sticking up into the “empty” headspace. The above sums it up pretty nicely as to why headspace is so important in canning.

In a nutshell, headspace is needed to allow for proper expansion of food when the jars are heated through processing, and for creating the vacuum seal when cooling. When heated to the high temperatures needed in canning, the air left in the headspace expands. The higher the temperature reached, the greater the expansion.

It should also be noted, that foods expand less than air when heated. Thus, when using a pressure canner, headspace requirements typically will increase.


As a general rule of thumb, plan on leaving the following headspace when canning these foods.

  • Jams & Jellies – 1/4 inch headspace
  • Tomatoes, Fruits, & Pickles – When water bath canning these food items plan on 1/2 inch headspace
  • Low Acid Foods – When pressure canning most low acid foods (think red meats, seafood, poultry, milk, and all fresh vegetables except for most tomatoes here) leave 1 inch headspace
  • Exceptions – As with any rule there are always a few exceptions. When canning some vegetables and meats, a 1/ 1/4 inch to 1 1/2 inch headspace may be required.

Note that too little headspace can result in “siphoning” or foods bubbling and leaking out when the air expands & is forced out with processing. Food particles may also prohibit the jar from sealing properly.

Too large a headspace and the foods within may discolor and the jar may not properly seal, creating a “false seal”, as the time allotted may not be enough to remove all the unwanted air.


You will have a couple of options for measuring your required headspace for canning. You can simply use a sterilized plastic ruler to determine your headspace or you can use a headspace measuring & bubble remover tool found in most canning tool kits.

It’s important to note that when filling your canning jars, all air bubbles need to be removed (using the opposite end of the headspace measuring tool or bubble remover) and the headspace properly measured prior to placing the two-piece caps or lids.

Headspace For Canning image showing quart size mason jar resting on wooden board with blurred greenery in background displaying a green headspace measurement tool resting on lip of jar


To measure your headspace using the headspace tool, the “steps” or ridges in the tool correlate with 1/4 inch increments reaching all the way to 1 inch.

Headspace For Canning image showing headspace measurement tool resting on wooden board with several empty mason jars and black arrows pointing to measurement steps

To use, place the appropriate measuring ridge on the side of the jar. The bottom edge of the headspace tool should just meet the top of the food line.


Need help managing all your canning efforts? Be sure to take a look at my affordable (and did I mention cute?) Canning Management Planner available to download in my Etsy Shop!

Canning Management Planner image showing 15 printable canning sheets for tracking and journaling all things canning related


To help you along with your processing efforts, I’ve created a unique FREE Canning Checklist cheatsheet listing all three methods of processing; pressure canning (article coming soon as well!), steam canning (instructional tutorial coming soon!), and water bath canning.

Print and laminate your copy of the Canning Checklist cheatsheet to use over and over again when processing! Simply use a washable marker to check off the list as you go! Once complete, wash the laminated list and you are ready for the next time you process!

Canning checklist cheatsheet listing pressure canning, steam canning, and water bath canning procedures which can be checked off as you process

Be sure to grab your FREE copy by clicking the button below 😊

Hopefully this has answered many of the common questions asked regarding headspace for canning. The importance of canning safely, & creating the exact required headspace for your safe canning recipe cannot be overly emphasized.

Have more questions? Let me know in the comments below & hopefully I can be of some help!

Did you find this tutorial on headspace for canning helpful?

Love, Light, & Laughter ~


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Jennifer Wise July 9, 2022 - 12:52 pm

This is very helpful. I’ve had the “bubbling out” occur now and again, so this will help!

Suzan Ferreira July 11, 2022 - 11:41 am

Thank you for stopping by, Jennifer! I’m happy you found this useful, and may all our hard earned product stay in those jars 🤗

Michele Morin July 6, 2022 - 12:02 pm

Good information! When I think about headspace in canning, I also think about leaving margin in my life.

Cindy Moore June 20, 2021 - 8:32 pm

Great info as usual! I don’t can so didn’t know how important the headspace is.

Danielle Ardizzone June 20, 2021 - 7:23 pm

I never heard of “headspace” in canning before. Good info!

Barbara June 17, 2021 - 11:58 am

Great instruction! Canning gives a feeling of accomplishment!

Allison Peteet June 16, 2021 - 6:09 pm

Great information. I envy those who can foods. I never learned how.

Kristen W Allred June 15, 2021 - 11:29 pm

I learned something new about canning. This looks like a neat tool.

Misskorang June 15, 2021 - 10:20 pm

Leave headspace when canning. Remember to leave headspace. Don’t forget headspace when canning.
I learned something new today.

Tiffany Smith June 15, 2021 - 8:36 pm

I think I have that tool but had no idea what it was for 😅

Cindy June 15, 2021 - 5:01 pm

This is so important. I remember learning about this in 4-H when we were canning for the fair.

Linda Egeler June 15, 2021 - 3:18 pm

We love canning tomatoes and salsa. This is a very timely post: more people seem to be interested in growing their own vegetables and in canning.

Cecile Leger June 15, 2021 - 1:48 pm

I knew not to overfill them, but I had no idea how important it was to keep them fresh. Thanks for these tips.

Kristin June 15, 2021 - 3:53 am

Haha, I’m such a rookie at gardening….I was thinking “yes, I’ve got to get in the right headspace for canning!” 😉 I’ve never done it but your posts are so informative and educational when I do!

Suzan Ferreira June 15, 2021 - 12:54 pm

😂 Too funny! Hope you can give it a try!

Marianne June 15, 2021 - 2:35 am

What an awesome little tool! I will have too look into getting me one! I just tend to eyeball it when I do my tomato sauce.

Alexis Farmer June 14, 2021 - 11:46 pm

Definitely going to revisit this when I start canning! Definitely don’t need botulism in my life.

Chelsea June 14, 2021 - 10:55 pm

I’ve canned once and I totally would need help to do it again. There were so many parts that required precision that I’d forget doing it on my own. And leaving headspace (and knowing how much to leave) would be one of those parts! Thanks for the detailed description and info. It’s always helpful!

Tiffany Gunther June 14, 2021 - 10:08 pm

I had no idea that headspace mattered for canning. Thank you for the information!

Sabrina DeWalt June 14, 2021 - 8:55 pm

I have seen this tool before but never realized what the ridges were for. So simple.

Stephanie June 14, 2021 - 4:22 pm

Great explanation! I have never heard Headspace for canning explained so clearly before.

Terra Booth June 14, 2021 - 4:10 pm

We love making our own pickles and jams, these are very important tips! Safety is our number one priority when we are doing this because we are well aware in our family that if you aren’t careful you can get sick from improper canning practices.

Suzan Ferreira June 15, 2021 - 12:57 pm

Happy to hear you are familiar with headspace and realize the importance of canning safely!

Erin June 14, 2021 - 3:14 pm

We used to can when we lived in Virginia. Now that we live in Tennessee, we have NO storage space AT ALL. I have so many supplies too! I’ve never heard of the headspace too – so cool!

Alicia June 14, 2021 - 2:45 pm

I didn’t realize how important headspace was! So interesting!


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