On flights between India, Pakistan and the Gulf, the weight is the easy part. Fifteen of the seventeen airlines in this guide set the cabin bag at 7 kg on their standard economy fare. Gulf Air allows 6 kg, and SalamAir, the only one that sells its cabin bag as an extra, allows 10 kg for the paid bag.
The size is where airlines differ
Qatar Airways allows a cabin bag only 50 cm long, 5 cm shorter than the common 55 cm. Gulf Air sets an unusual box of 45 × 40 × 30 cm: shorter still, but deeper than anyone else. IndiGo limits the width to 35 cm, and Air India, flydubai, Air Arabia, flyadeal and Jazeera Airways stop the depth at 20 cm. A case that passes on Saudia or Kuwait Airways, which accept 56 × 45 × 25 cm and more, can fail on any of these.
Akasa Air and Oman Air give only a total: length, width and height together may not exceed 115 cm. airblue writes its limit in inches, 22 × 15 × 8 in, or about 55.9 × 38.1 × 20.3 cm, with a 45 in total.
The second bag is not always free
Air India, Akasa Air and Air Arabia allow a personal item of up to 3 kg next to the 7 kg bag; on Air Arabia both count within a 10 kg total that includes duty-free shopping. flynas allows one cabin piece per guest and charges for any additional piece, so a laptop bag carried next to the case can cost extra. SalamAir's free bag is a 25 × 33 × 20 cm piece of up to 5 kg.
Rules that depend on the route
Emirates sets a 115 cm total for passengers boarding in India. IndiGo says its allowance varies by flight and that the details on the booking confirmation take priority over its general page. flynas also asks for a liquids bag of 500 ml at most, half the one-litre bag many travellers use.
One bag for the whole corridor
The figures below give the largest bag that all seventeen accept (on SalamAir only as the paid bag). It is small, because Gulf Air cuts the length to 45 cm, IndiGo the width to 35 cm, and five airlines the depth to 20 cm. If you know your airlines in advance, check them in the table rather than packing to the smallest box.