How to measure jam jar lids - Wares of Knutsford
Posted by The Wares Team on 27th Feb 2023
We often hear from customers who have bought some glass jars and bottles but need some replacements lids in order to re-use or re-purpose them. The specific measurements of the jar finish and of the lid finish matter! Be sure you are choosing the lid which is compatible with the jar.
Understanding jar lids
Firstly it is important to identify if the closure has a continuous thread or a lug:
Continuous thread is the Mason-style closure where is the jar and lid are both threaded in one continuous bead/thread around the entire circumference of the opening also known as a screw on lid. All of our Mason jars have this type of neck.
Lug is the closure system where the container has multiple threads and the lid has an equal number of lugs or tabs that grip the corresponding threads, also known as twist off closures. This is the type of neck and lid that you are probably familiar with and can be seen on any typical supermarket jam jar.
How to measure a glass jar to get the right lid
Measurements for jars and lids are almost always in millimeters (mm). When measuring the neck of the jar, you will need to measure across the diameter from the outer edge of the glass on one side to the outer edge of the glass on the other side. The diameter of the jar will be approx. 3mm smaller than the lid you require. For example if the neck of your jar measures 79mm, the lid size you require will be 82mm.
How to measure jar lid size
If you are in possession of the correct lid to fit your jar, but need to know what size it is to order some more, you need to measure again across the diameter of the lid, but this time you are measuring from the inner edge of the lid to the inner edge of the lid on the other side with the lid upside down.
Our standard lug jam jar lids:
38mm 43mm 48mm 53mm 58mm 63mm 66mm 70mm 82mm