We are not brewers here but we have dabbled with small brewing kits which supplied us with 50g of hops for a 50 pint keg. How much beer you make will of course depend on your recipe and how many hops you will be adding to your brew.
How many grams of hops per plant?
Your hop yield will vary according to your variety and its growing condition. Hop plants will also be getting establish during their first two growing seasons, reaching their full potential in their third year. By the third year you could get around 400-500g of dried hops per plant (a rough calculation shows we yielded 430g of dried hops per plant in our hop gardens).