Canning Jar Sizes and Mouth Widths: A Plain Guide

Canning jars come in two mouth widths and a handful of standard sizes. That sounds simple until you're in a store aisle choosing between a dozen boxes. This guide explains each size and opening, which lids fit, how jar size ties into processing time, and the jar-prep rules from the USDA Complete Guide to Home Canning as published by the National Center for Home Food Preservation (NCHFP).

The one rule that matters most

Use the jar size your tested recipe names. Processing times are worked out for specific jar sizes, because heat takes longer to reach the center of a bigger jar. NCHFP's processing-time guidance notes that quart jars generally need more time than pints in a boiling-water canner.

There's one helpful shortcut. In the USDA guide's tables, process times for ½-pint and pint jars are the same, and so are times for 1½-pint and quart jars (NCHFP). That applies to USDA tables. Other recipe sources may lay out their tables differently, so read the recipe in front of you.

Regular mouth vs. wide mouth

Every standard home-canning jar has one of two openings. NCHFP describes the standard (regular) jar mouth as about 2⅜ inches across and wide-mouth jars as about 3 inches, "making them more easily filled and emptied." Accessory makers often list the outer diameter of the threads instead. Masontops, for example, gives 2.75 in (7 cm) for regular and 3.38 in (8.6 cm) for wide (size guide).

Lids aren't interchangeable between the two widths. Because the two openings are standard, though, regular lids from one major brand generally fit another brand's regular-mouth canning jars. Check the box for compatibility.

Standard sizes and what they're for

NCHFP lists Mason-type home-canning jars in ½-pint, pint, 1½-pint, quart and ½-gallon sizes, plus regular-mouth decorator jelly jars in 8- and 12-ounce sizes.

How many jars fit in a canner?

Canner capacity is usually given in jars, and it depends on size and mouth width. NCHFP's general guidance is that most canners hold seven quart jars or eight to nine pints. Small pressure canners hold four quarts, and some large pressure canners hold 18 pints in two layers but still only seven quarts.

A concrete example: Presto's spec sheet for its 23-quart pressure canner (No. 01781) gives these capacities, and they show how much depends on method and mouth width:

Plan your jar purchases around a full canner load of your favorite size, and remember that quarts need the tallest pot.

Lids: what fits and what's reusable

• Match lid size to the mouth: regular or wide.
• Use new flat lids every time. NCHFP says Mason jars can be reused many times "requiring only new lids each time."
• Bands are reusable when clean, dry and not rusted or bent. NCHFP recommends removing them from cooled, sealed jars before storage.
• Buy only about a year's supply of lids. NCHFP says the gasket compound in unused lids works well for at least 5 years from manufacture, and older lids may fail to seal.

Do jars need to be sterilized?

Often not. Per NCHFP's jar guidance:

• Sterilize empty jars for jams, jellies and pickled products that will be processed less than 10 minutes. Put the jars upright on the rack in a boiling-water canner, fill the canner and jars with hot (not boiling) water to 1 inch above the tops, and boil 10 minutes at elevations under 1,000 ft. Add 1 minute for each additional 1,000 ft.
• No presterilizing is needed for jars that will be pressure-canned, or for fruits, tomatoes and pickled or fermented foods processed 10 minutes or longer in a boiling-water canner.
• Either way, wash jars in hot water with detergent and rinse well, by hand or in a dishwasher. NCHFP notes that washing doesn't sterilize. Hard-water film can be removed by soaking jars for several hours in 1 cup of 5% vinegar per gallon of water.

Can I reuse store-bought jars?

NCHFP says most commercial pint- and quart-size mayonnaise or salad-dressing jars can be used with new two-piece lids for acid foods, but you should expect more seal failures and breakage. They have a narrower sealing surface and are tempered less than Mason jars. They're not recommended for pressure canning. Other commercial jars that can't take a two-piece canning lid (pasta sauce jars with one-piece lug caps, for example) aren't recommended for home canning at all.

Inspecting jars before each batch

• Run a finger around the rim. A nick or chip can stop a seal.
• Look for cracks and deep scratches. NCHFP warns that seemingly insignificant scratches can cause breakage in the canner.
• Retire jars that have been used for non-food purposes or that you can't identify as canning jars.

Storing filled jars

Jar size also affects how you store and use what you've canned. NCHFP's storage guidance covers it:

• Remove screw bands once jars have cooled, then wash, label (contents and date) and store the jars in a clean, cool, dark, dry place. NCHFP gives 50°F to 70°F as the best temperature range.
• Don't store jars above 95°F or near hot pipes, a range or a furnace, in an uninsulated attic, or in direct sunlight.
• For best quality, NCHFP advises canning no more than you'll use within a year, unless a specific food's directions say otherwise.
• Smaller jars mean less waste after opening, since an opened jar has to be refrigerated.

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Quick answers

Are wide-mouth jars better?

They're easier to fill and clean, which matters for packed foods. Regular mouth is fine, and cheaper per lid in many stores, for jams, sauces and juices. Your recipe's process time applies either way unless the recipe specifies a mouth style.

Can I can in half-gallon jars?

Only very acid juices such as apple and grape, per NCHFP. Don't use them for vegetables, tomatoes, fruit pieces or anything else.

Do 12-oz jars use pint times?

Use whatever your tested recipe says for that jar. If it doesn't list the 12-oz size, use a size it does list.

Related: Water-bath vs. pressure canning · Beginner equipment checklist

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