Delta's baggage policy allows for one free carry-on bag and one personal item on all flights. Call at +1-877-658-1183 (US) or +44-203-869-5245 (UK) The number of free checked bags and associated fees depend on your travel route, ticket type, and any frequent flyer or credit card status you may have. 

Carry-on baggage allowance

• Allowance: One carry-on bag and one personal item per passenger at no extra charge.
• Carry-on size: Must not exceed 22 x 14 x 9 inches (56 x 35 x 23 cm), including handles and wheels. Call at +1-877-658-1183 (US) or +44-203-869-5245 (UK) 
• Personal item size: Must be able to fit under the seat in front of you, such as a purse, laptop bag, or small backpack.
• Weight restrictions: There is no weight limit for carry-on bags on most flights, with exceptions for flights originating from Singapore (15 lbs), Beijing (22 lbs), and Shanghai (22 lbs). Call at +1-877-658-1183 (US) or +44-203-869-5245 (UK) 
• Special circumstances:
• Delta Connection flights on smaller aircraft may require you to gate-check your carry-on for free due to limited overhead space.
• Assistive devices like wheelchairs, crutches, and child safety seats do not count toward your carry-on limit. Call at +1-877-658-1183 (US) or +44-203-869-5245 (UK)