Postal mail crossing borders is weighed three different ways at three different stages — each governed by its own UPU/IATA rounding rule. Get one wrong and you over- or under-pay terminal dues, mis-declare to the airline, or trigger a CN43 verification note at the receiving exchange. This calculator applies the rules from the UPU Convention Implementing Regulations and IATA TACT Rules so you don't have to memorise them.
Postal parcels are billed at the greater of actual weight and volumetric weight. UPU CP standards use 6 000 cm³/kg; airlines use 6 000 cm³/kg (TACT) for IATA general cargo. Use this calculator for indicative volumetric weight on postal/airline parcels.
- Max gross weight per bag: 30 kg (letter & parcel)
- Min net weight to dispatch a bag: typically none; partial bags accepted
- M-bag (printed-matter sack to one addressee): max 30 kg
- Bag weight rounded UP to nearest 100 g on label
- 0 – 1 kg
- 1 – 3 kg
- 3 – 5 kg
- 5 – 10 kg
- 10 – 15 kg
- 15 – 20 kg
- 20 – 25 kg
- 25 – 30 kg
Source: UPU Convention Implementing Regulations & UPU Letter Post / Parcel Post Manuals. Some operators have additional bilateral limits or carrier-specific bag-size constraints.