You packed to exactly 23 kg, but the check-in counter still flagged your bag. The problem is rarely the scale: it is that “23 kg” means different things on different tickets, and suitcase size is not measured the way most people think.
Why “23 kg” is not a universal rule
Your baggage allowance is simply the amount of luggage an airline lets each passenger bring, in the hold or in the cabin. It varies by airline, cabin class, elite status, ticket type, origin and destination. Even two flights on the same booking can follow different limits, for example when one of them is a long-haul leg. The exact conditions are written in your ticket information online, and that is the only number that really counts.
The 23 kg figure most travellers remember comes from the International Air Transport Association (IATA), which recommends a maximum of 23 kg (50.7 lb) per checked bag, with a hard limit of 32 kg (70.6 lb). The 23 kg ceiling exists because of health and safety regulations. But it is a recommendation, and airlines follow it fully, partially or not at all.
Piece concept vs weight concept
Airlines use two different systems, and mixing them up is where most surprises come from.
- Piece concept: you may check a set number of suitcases, each up to 23 kg in Economy (32 kg in Business or First). It traditionally applied to flights to or from the Americas, and Vietnam Airlines adopted it on 1 August 2019.
- Weight concept: you get a total weight, no matter how many bags it is spread across. Passengers travelling together can often combine their allowances.
So under the piece concept, 23 kg is a per-bag cap. Under the weight concept, it can be a total for everything you check.
A real example with two travellers
Say two friends fly together with one suitcase of 26 kg and another of 14 kg, 40 kg in total.
On a piece-concept ticket with one 23 kg bag each, their combined allowance is 46 kg, so the total is fine. But the 26 kg suitcase is 3 kg (about 6.6 lb) over its own cap, and every bag is weighed separately at check-in. The fix is simple: move 3 kg into the lighter bag, giving 23 kg and 17 kg.
On a weight-concept ticket with, say, 25 kg per person that can be pooled, the pair can check 50 kg together. Their 40 kg passes, and the 26 kg suitcase is not a problem on its own because only the total matters.
Same bags, same scale, two opposite outcomes. That is why the first thing to check is which concept your ticket uses, not just the number.
Suitcase size is the sum of three numbers
Size limits for checked bags are usually given as a total linear measurement: length + width + height, added together. IATA advises a maximum of 158 cm (62.2 in), with an absolute limit of 203 cm (about 80 in).
A suitcase of 75 × 50 × 30 cm adds up to 155 cm, just under the 158 cm guideline. A slightly bigger one at 80 × 55 × 30 cm reaches 165 cm: still under the 203 cm hard limit, but above the recommended size, so some airlines may treat it as oversized.
Cabin bags are judged mainly by size rather than weight. IATA’s 2015 recommendation is 55 × 35 × 20 cm, and bags meeting it can carry the “IATA cabin OK” logo. Because that is tighter than most airline limits, such a bag is accepted almost everywhere. European airlines typically allow around 56 × 41 × 20 cm and 6.8 to 10 kg, but this varies.
Common mistakes before you fly
- Measuring only the length. A bag that “looks” average can exceed 158 cm once all three sides are added.
- Assuming every leg has the same rules. Connecting flights and different carriers on one ticket can change the allowance.
- Forgetting low-cost fares. Carriers such as Ryanair and AirAsia charge for checked bags, while full-service airlines usually include them.
- Packing a power bank in the hold. Spare lithium-ion batteries, including power banks, are not allowed in checked baggage. Keep them in your cabin bag.
If you are still over at the counter, you will usually have to shift items to another bag or into your carry-on. Excess baggage is carried at the airline’s discretion for a fee, with no guarantee, and on some routes it may not be accepted at all.
