When it comes to men's necklace lengths, the most common length ranges between 18" to 24". With this length, the pendant and the chain will rest slightly below your collarbone. Anything shorter than 16-inches borders with the choker category.
The length you go for will significantly depend on your style. Longer chains (24-30-inches) offer a relaxed look and are ideal for a night out or weekends. Shorter chain lengths pair well with formal outfits like shirts.
Your height matters a lot when it comes to the length of the chain. Shorter people look better with average and shorter chain lengths and should avoid overly long chains.