Cabin Baggage Rules and Size Limits Explained | Turkish Airlines

What the official page says

Economy: one cabin bag max 23 x 40 x 55 cm (55 x 40 x 23 cm) and 8 kg, plus one personal item 40 x 30 x 15 cm and 4 kg. Business: two cabin bags each 23 x 40 x 55 cm (55 x 40 x 23 cm) at 8 kg each (16 kg total), plus one personal item 40 x 30 x 15 cm and 4 kg.