Please be guided, because of the variance in sizes of pearls and knotting, lengths/pearl size of items could vary by up to .5in/.5mm.

Although the market and the pearl jewelry industry has evolved certain standard lengths and categorized them with beautiful names but one is not limited to selection based upon them. Every woman has her own taste and style.                                                    

Pearl Collar ~ 12 to 13 inches
These lengths are normally made up to 3 strands to snugly fit high around the neck. They were very popular during Victorian era and are now again in fashion.                                  
Pearl Choker ~ 14 to 16 inches
They are similar to collar but hang little lower on the neck. They look very fine both for casual and formal eveningwear.            
Princess Necklace ~ 17 to 19 inches
A very classic and versatile length indeed. This style length is neither short nor long and is preferred choice of many women.
Matinee Necklace ~ 20 to 25 inches    
They are good for casual, business or semi-occasions attire and are very traditional. The extra length of matinee necklace gives the appeal of luxury and sophistication.    
Opera Necklace ~ 26 to 36 inches                              
They fall below the bust line, good for formal evening occasions and go very well with evening dresses. Best is they can also be worn as double strand too. Woman has the luxury of choosing her own style.                                   
Pearl Rope ~ 37 inches or longer