The minimum legal weight of the senior men’s Olympic javelin is 800 grams.
The men’s javelin is also regulated by dimensions: the implement is generally about 2.6 to 2.7 metres long, with a metal head and a grip wrapped around its centre of gravity. Competitors throw it from a runway and must release it before crossing a curved foul line. The javelin must land tip-first within the marked sector for the throw to count.
Women’s senior javelins weigh 600 grams, so the two implements should not be confused. The men’s javelin was redesigned in 1986 because athletes were throwing so far that sector boundaries and landing safety became serious concerns. The redesign moved the centre of gravity forward, causing the javelin to descend more steeply and reducing typical distances. A throw is measured from the foul line to the nearest mark made by the tip, not to the point where the athlete’s body or grip ends.