Which throwing event uses a 2.5 m diameter circle?

The discus throw uses a 2.5-metre-diameter throwing circle.

The athlete spins inside the circular enclosure before releasing a heavy, flat disc into a marked landing sector. The throw counts only if the discus lands inside that sector and the competitor leaves through the rear half of the circle after the implement has landed. Touching the top of the rim during the attempt is also a foul.

The circle’s diameter is a useful way to distinguish the discus from other throwing events. The shot put and hammer throw use smaller circles measuring 2.135 metres in diameter, while the javelin is launched from a runway rather than a throwing circle. The discus landing sector is currently marked at an angle of 34.92 degrees.

Standard senior men’s discus weighs 2 kilograms and measures about 22 centimetres across; the women’s discus weighs 1 kilogram and is about 18 centimetres wide. The event combines rotational speed, balance and release angle rather than simply arm strength.