The chain size refers to the "wire diameter" or width of the metal used to make a link, as shown above. However take note, if you're looking to replace or extend your chain you also need to consider the other dimensions as chains can differ in length, width, and pitch (inner length) depending on your gypsy.

The best thing to do is measure 5 links, but not at the joint, and take an average. For the other dimensions the tables at the bottom of the page will give an indication of what your chain is likely to be.

Calibrated marine chain is made to specific dimensions (wire diameter, pitch, width) to ensure it will be gripped correctly by the gypsy (the notched ring that meshes with the links) in your windlass. There are a variety of coded calibration... for metric the ones you should be looking for are DIN766 and ISO4565.

Our chain markers are made with tolerances to fit all calibrated chains, so may be slightly lose on some chains, but this will not effect their performance.

The best and most accurate way to measure the chain will be with a set of calipers. You simply need to measure the diameter of a number of the chain link sides to get a good average, this will give you a pretty accurate measurement. Bear in mind old chain may have slightly deformed links due to the mechanical stresses they are under so the measurements you get may not be an exact match.

If you only have a tape measure or ruler the easiest way to measure your chain size will be to measure the diameter of one of the link sides as accurately as you can as per the picture and then use the table to confirm the overall link size which will be pretty standard for marine chain. Also use the DIN766 table measuring other dimentions of the chain link to find out what size you're using.