I came across this interesting piece of information online.
Question: “How do pilots determine the weight of a passenger flight before take off?”.
Answered by a pilot: "Ok. Follow carefully. Terminology varies from country to country, but principles do not.

The “empty weight” of the aircraft is known, quite accurately, from actually putting the thing on big scales (one wheel at a time, if necessary).

If an airliner, the “dry operating weight” is known. This is the empty weight, plus the weight of all catering and passenger service packs, plus the weight of the crew (using standard weights there), plus the weight of any special equipment routinely carried (such as life rafts, first aid kits, etc.)

The weight of the fuel on board is known very accurately.

Everything in the baggage hold  freight, mail, checkedin luggage  is weighed before being put in. This is partly to avoid overloading the aircraft, and partly to ensure it’s not too nose or ailheavy.
That just leaves the passengers  also known as punters, selfloadingfreight, and a few other terms we need not explore here.

Passengers are assumed to weigh a certain amount. Different countries use different weights for men, women, children and infants. Different countries use different methods of accounting for carryon luggage. But there will be a statistical methodology in place, and it will be checked for statistical accuracy about once a decade or so. (People are heavier in the USA than in Japan. People are heavier now than they were in the 1950’s. And so on.)

For departure airports that are known to be very restrictive, such as (in my case) departures from the short and severely restrictive runway at Lord Howe Island, standard weights are not used; we weigh everyone and everything. Usually, this results in more people being carried, as the standard weights tend to be conservative.
All up, the weight figure placed in front of the captain should be either less than, or no more than 1% more than the actual weight of the aircraft if you put it on scales. This degree of error is tolerable in all possible circumstances.".
Is this correct?
I’d appreciate it when real life pilots would weigh in (pun intended) and confirm this.