Short answer: there’s no single universal allowance — baggage rules for Colombo (CMB) → Dubai (DXB) depend on the airline, the cabin/fare you bought, and whether the ticket is codeshare. Below are the typical allowances for the main carriers on that route (checked and carry‑on). I’ve cited each airline’s official policy.

• Emirates

  • Checked (weight concept on CMB–DXB): Economy fares typically range (Special 20 kg, Saver 25 kg, Flex 30 kg, Flex Plus 35 kg); Business 40 kg; First 50 kg. Each bag must not exceed 32 kg. (emirates.com)
  • Carry‑on: Economy 1 piece up to 7 kg (55 x 38 x 22 cm); Business/First allow 2 pieces (briefcase + handbag/garment) up to 7 kg each (combined limits vary by class). (emirates.com)

• SriLankan Airlines

  • Checked: Economy normally 2 pieces up to 23 kg each (piece concept on some routings/partner tickets can differ); Business/First allowances higher (pieces up to 32 kg each) — check your ticket for the exact allowance. (srilankan.com)
  • Carry‑on: Generally Economy 1 piece up to 7 kg; Business 2 pieces up to 7 kg each (dimensions per airline rules). (seatmaestro.com)

• flydubai

  • Checked: Economy fares are sold with pre‑paid checked baggage options (commonly 20, 30 or 40 kg depending on fare purchased); Business allowance commonly 40 kg. You must check your fare to see which weight you have. (flydubai.com)
  • Carry‑on: Economy 1 piece up to 7 kg (55 x 38 x 20 cm); Business up to 2 pieces totalling 14 kg (7 kg each). (flydubai.com)

• Air Arabia (and other low‑cost carriers)

  • Many LCCs flying nearby (e.g., to Sharjah) use paid baggage pricing: you typically choose/ buy a checked weight (20/30/40 kg) when booking. Hand baggage allowances are small (Air Arabia: carry‑on + personal item up to ~10 kg combined). Confirm at booking. (book.airarabia.com)

Important notes

• Codeshares / interline itineraries: the operating carrier’s baggage rules usually apply — always check your e‑ticket/itinerary which shows the operating airline.
• Size/overweight/oversize fees vary by carrier and airport; some carriers enforce strict per‑piece weight limits (e.g., 32 kg). (emirates.com)
• Airline policies change — for the exact allowance on your booking, open your ticket/PNR or the airline’s “Manage Booking” page or check your e‑itinerary. If you tell me the airline and fare class (or forward the booking line), I can look up the precise allowance for your ticket.