B747-400 first officer reported they departed with incorrect cargo weight information; resulting in ...

Narrative:

We departed for our flight and was notified several hours later via sat [phone] that [air carrier] had discovered a mistake in the manner in which it calculated our cargo weight. They discovered that their operator incorrectly measured several pallets resulting in a lower than actual weight. After being notified by our company; it was decided to return to [origin]; our departure airport. We requested and company provided new burns and a much higher zero fuel weight (approximately 45;000 lbs). After reading the 'overweight policy' in the QRH; and taking other factors into account; we decided to dump our fuel to 60;000lbs remaining. This would give us a landing weight of 625;000; well below our max landing weight.landing and taxiing were uneventful.it is very difficult to state what as a crew we would have done differently to prevent this situation. We rely on many different people to do their jobs correctly to ensure we have a safe flight. There is very little we could have done in this situation short of standing next to the scale operator to ensure he/she was preparing weight tags properly.

Original NASA ASRS Text

Title: B747-400 First Officer reported they departed with incorrect cargo weight information; resulting in a much heavier gross weight than planned for. They returned to departure airport.

Narrative: We departed for our flight and was notified several hours later via SAT [phone] that [air carrier] had discovered a mistake in the manner in which it calculated our cargo weight. They discovered that their operator incorrectly measured several pallets resulting in a lower than actual weight. After being notified by our company; it was decided to return to [origin]; our departure airport. We requested and company provided new burns and a much higher zero fuel weight (approximately 45;000 lbs). After reading the 'Overweight Policy' in the QRH; and taking other factors into account; we decided to dump our fuel to 60;000lbs remaining. This would give us a landing weight of 625;000; well below our max landing weight.Landing and taxiing were uneventful.It is very difficult to state what as a crew we would have done differently to prevent this situation. We rely on many different people to do their jobs correctly to ensure we have a safe flight. There is very little we could have done in this situation short of standing next to the scale operator to ensure he/she was preparing weight tags properly.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1246210
Time
Date	201503
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Procedural Published Material / Policy Deviation - Procedural Weight And Balance

B747-400 first officer reported they departed with incorrect cargo weight information; resulting in a much heavier gross weight than planned for. They returned to departure airport.