Estimate how much firewood you need for a heating season.
Firewood is bought by volume but burned by weight, so the estimate has to cross between the two. Total weight comes from the burn rate and the hours you burn. Dividing by the wood's density gives solid volume, but a stack is roughly 30% air, so the stacked volume you must store and pay for is higher. A cord is a fixed 3.6246 cubic metres of stacked wood, which is why denser hardwood delivers far more heat per cord than softwood.
Total weight
kg = weeks x 7 x hours per day x kg per hour
Stacked volume
stacked m3 = (kg / density) / 0.7 (a stack is about 30% air)
Cords
cords = stacked m3 / 3.6246
Because heat comes from mass, not volume. Softwood is about 35% less dense than oak, so the same cord holds proportionally less fuel and you need more cords for the same season.
Yes, and badly. Green wood can be half water by weight, so much of the energy goes into boiling that water off instead of heating the room. Season wood to under 20% moisture before burning.