Plus there are sooooooooooooo many variables that affect weight of base van!
4Motion? LWB/SWB? Wheels? Lined? Sound-deadened? Retrofit ICE system?
Only way to tell is to attract the attention of the local bobby who hauls you to the nearest weighbridge when you're empty OR go there voluntarily and slip the geezer on the gate something with the king's head on to let you sit on his scales for a moment!
Privately owned (vs council owned) waste disposal/recycling places are quite accommodating I've found!