From DARTS REGULATION AUTHORITY RULE BOOK:
- GENERAL PLAYING RULES
- 5.1 Administration
- 5.1.1 Players shall provide their own darts which shall not exceed an overall maximum length of 30.5 cms (12ins) nor weigh more than 50 grams. Each dart shall consist of a needle shaped point which shall be fixed to a barrel. At the rear of the barrel
shall be an attached flighted stem which may consist of up to a maximum of three separate pieces (namely any combination of; a flight, a flight securing device and a stem).
So, weight limit for darts is 50 grams.
You can find about dart information of a player using dartsdatabase.co.uk.
From perfectdartsforum post "Average Dart Weight of the Top 32 PDC Players" average was found to be 22.09 grams. (might have changed so use dartsdatabase.co.uk)
Fro dartworld.com post "Helpful Information"
Steel tip darts are measured by weighing the point and barrel without the flight and shaft. Although darts are available in a wide range of weights (from 18 – 40 grams), the majority of players play with darts weighing 18 – 23 grams when using brass and 23 – 26 grams when using tungsten darts. The legal weight limit of your major overseeing organizations is 50 grams.
Soft tip darts are measured by weighing the entire dart including the barrel, flight and shaft. The weights being used to play soft tip darts are most commonly 16, 18 and 20 grams and are much lighter than their steel tip counterparts. Originally, soft tip darts needed to be light in weight because the electronic matrix in the vending machine was delicate and couldn’t withstand the impact of a heavy dart. The technology has been greatly improved over the years and the dart weights have increased steadily from the original 12 grams to the current top weight of 20 grams.
Other source: http://dartbrokers.com