A 4 oz glass jar takes a 58/400, 70-450, or 37 mm lid depending on its neck finish — the thread diameter, not the jar’s capacity, decides the fit.
Two jars that both hold four ounces can wear lids nearly an inch apart in diameter. Capacity tells you nothing about the threads, and that gap is why so many replacement lids bought online end up rattling loose or refusing to start. Manufacturers say it outright: jar volume, in ounces or milliliters, does not determine lid size. The only reliable match is the jar’s neck finish, a two-part number stamped into every jar spec. Read that number and covered here is exactly how to measure it when no stamp exists.
What Do the Numbers on a Jar Lid Mean?
A finish code like 70-450 reads as two measurements: the first number is the opening’s outer thread diameter in millimeters, and the second is the thread style and depth. Thread diameter is measured across the outside of the jar’s threads — never the body, never the inside, never the fill volume. That single rule resolves most of the confusion, because the code describes the glass itself.
The most common finishes across US jar manufacturing include 33-400, 38-400, 53-400, 63-485, 70-450, 82-2040, and 89-400. The “400” family is the workhorse continuous-thread standard for small jars; larger second numbers like 2040 describe heavier, deeper thread profiles. When a listing says 58/400 or 70-450, it is naming the finish, not the jar’s capacity.
Some 4 oz jars step outside those standards entirely. One round faceted 4 oz jar is listed with a 37 mm opening and a plastisol-lined lid. So a lid that threads perfectly onto your neighbor’s 4 oz jelly jar may never catch on yours.
What Size Lid Fits the Common 4 oz Jar Styles?
The four documented 4 oz examples below cover the vast majority of what US buyers actually receive: 58/400 on straight-sided jars, 70 mm and 70-450 on mason styles, and 37 mm on faceted jars. Matching your jar’s style to this list is the fastest check, but confirm against the finish code before buying more than a single lid.
| 4 oz Jar Style | Documented Closure Size | Lid Type & Liner |
|---|---|---|
| Straight-sided clear glass | 58/400 | Black plastic continuous-thread lid |
| Eco mason tapered | 70 mm | White metal continuous-thread, plastisol lining |
| Tapered glass mason | 70-450 | Continuous-thread lid, plastisol lined |
| Regular-mouth quilted jelly mason | 70 mm regular mouth | Regular Mouth lid; wide-mouth lids do not fit |
| Round faceted | 37 mm opening | Plastisol lined, BPA-free lid |
| Generic 4 oz jar, no stamp | Measure the threads first | Match lid to measured finish code |
How To Measure a Jar Lid Size Without a Finish Code
Measuring takes about a minute with a ruler marked in millimeters. If your jar carries no printed finish code, the thread measurement is the answer — and it beats guessing from pictures every time.
- Remove the existing lid and set the jar on a flat surface.
- Lay a millimeter ruler straight across the widest point of the jar’s threads — the raised spiral just below the opening rim.
- Read the outer diameter in millimeters. A reading near 58 points to 58/400; near 70 points to 70-450 or another 70 mm finish; near 37 points to a 37 mm opening.
- For continuous-thread or lug lids you’re measuring separately, measure across the inside of the lid instead, then compare that number to the jar’s thread diameter.
- Write the finish code on the jar’s underside with a marker so the next lid order takes seconds.
That measurement habit is exactly what the roundup of tested 4 oz glass jars with lids saves you from, since each pick there already ships with its matching closure.
Once you have the number, buy by finish code rather than by the phrase “4 oz lid.” A listing that names 58/400 or 70-450 is telling you the geometry; a listing that only says “small jar lid” is telling you nothing. Fillmore Container’s measurement guide lays out the same measure-the-threads rule this section follows: Fillmore Container’s jar and lid measuring method.
Two Lids That Measure the Same Can Still Seal Differently
Diameter is only half the match — the liner decides whether the seal actually holds. Foam, pressure-sensitive, and induction liners each perform differently against the same glass, which matters most for canning, gifting, or anything stored upside down. Several 4 oz jars ship specifically with plastisol linings, the soft PVC gasket that softens against hot contents and grips the rim.
Two more mismatches worth knowing before checkout:
- Regular versus wide mouth is a hard split. Wide-mouth lids will not fit regular-mouth jars — the 4 oz quilted jelly jars are regular mouth and explicitly reject wide-mouth caps.
- Metal for processing, plastic for pantry. Metal continuous-thread lids with plastisol linings suit heat processing and long storage; plastic lids are fine for dry goods and everyday reopening.
Buy the finish code first, then choose the liner for what the jar will actually hold.
FAQs
Can I use a wide-mouth lid on a 4 oz regular-mouth jar?
No. Wide-mouth lids and regular-mouth jars use different thread diameters, and product documentation states plainly that wide-mouth lids will not fit regular-mouth 4 oz jars. Regular-mouth jars take 70 mm closures; wide-mouth closures are larger across the threads regardless of how similar the jar capacities look.
Why do two 4 oz jars need different lids?
Because capacity describes volume while the lid matches the neck finish — the outer diameter of the glass threads. A 4 oz straight-sided jar may use 58/400, a 4 oz mason-style jar may use 70-450, and a faceted 4 oz jar may use a 37 mm opening. Same volume, three different lids.
Do I measure the jar opening or the old lid?
Measure the jar’s threads across their outside diameter in millimeters for continuous-thread finishes, then match that number to the finish code. If you are measuring a loose lid instead, run the ruler across the inside of the lid. The jar’s threads are the more reliable reference since every replacement lid must meet them.
References & Sources
- Fillmore Container. “How to Measure Jars and Lids for the Perfect Match.” Supports the thread-measurement method and matching measured finish codes to lids.
- The Cary Company. “Jar Lid Size Chart: A Complete Guide to Choosing the Right Lid.” Supports the common neck finish list and liner performance notes.
- Specialty Bottle. “4 oz Eco Mason Tapered Glass Jar with 70 mm White Metal Lid.” Documents a 4 oz jar’s 70 mm continuous-thread closure and plastisol lining.