Hard cider

If I want to make hard cider and use honey instead of sugar how much honey should I use (recipe calls for 2lbs of sugar to 1gal of apple juice)

That sounds fine, but you will have a sky-high ABV which will need a while to mellow out. Honey is around 80% sugar, so follow a normal recipe (or look for a 'cyser' recipe) and sub this in.

2 lbs is way too much sugar. It will take long time to mellow out. I tend to use less than a lot of people, but use aout 0.25 lbs to a gallon. That takes me to about an OG of 1.060, which will end up with a dry cider of around 8% abv. I like to use an ale yeast as I think it leaves more flavor.

However .... to answer your question. Honey has about 36 gravity points to a pound, while sugar has 45 (46 actually, but the numbers are easier using 45). Thus 1.25 lbs of honey provides the same amount of fermentable sugars as 1 lb of sugar.

Additional notes: 1) Honey takes a long time to ferment out (months), so be prepared to wait a long time. 2) Adding honey will give you a Cyser, not Cider. 3) 2 lbs of sugar + 1 gallon of juice will give you an OG of about 1.140. If you manage to ferment it to dryness, it will get to about 18 to 19% abv. Most yeasts will die before it gets that far, so be prepared for a sweet cider that will not carbonate. If you do go with this amount of sugar, do not use an ale yeast, otherwise it will be unbearable sweet; ue a high alcohol tolerance wine yeast.