I have made thirteen pint jars' worth. Whether that equates to thirteen pounds, I do not know. They say over here that a pint's a pound all the world round, which is of course nonsense; any true-born Brit knows that a pint of water weights a pound and a quarter. I know I had just under ten pounds of fruit, so I used just under ten pounds of sugar. And maybe four pints of water (I chickened out; I boiled the whole oranges last night in two batches, using the same water, thinking to start with lots less than usual and so not need to cook it so long; but I lost my nerve when I was dissolving in the sugar this morning, and added another couple of pints). If I had any empty jars, I could do the sums with my scale, but I had to rout out an extra for the thirteenth anyway, and lord only knows where the rest of my empties are.
Anyway: we have more marmalade than we have room to store, which means more than we need. Anyone local want a jar? It's dark, chunky, mature, and shouldn't be too sweet despite all that sugar. (I tasted a Seville once, just to know. They are lovely, but yup: as bitter as you think, and maybe then some.)