how long is a piece of string ?
It all depends on how far you want to take self sufficiency .... which really doesn't exist anyway . Self reliance is nearer the mark .
If you want to grow all of your own veg , then an old sized allotment would grow enough food for 4 people . That size was 90' x 30' . However you have to be very efficient with your veg , and have no losses etc etc ...and that doesn't happen . You therefore should double that size , at least , and have much more than you need . You can then sell , barter or give away surplus veg.
Food for your dogs is more difficult . Do you want to feed them meat ? or veg? or a mix ? Whatever , you have to grow or rear it , or swap/barter for the surplus veg.
If you want meat for yourselves then you need to work out the area you need to supply that . You can use as a very rough guide 5 sheep to the acre and one cow to the acre . In reality you need more than that area as you need to grow hay for the winter. If you have sheep you get the wool for jumpers , hats , gloves , scarves etc etc as well as carpets, and if you weave , cloth too . A fleece can be anything from 3 lb to 10 lb or a bit more , dependent on variety . So it is easy to work out from that and your needs , the amount of jumpers etc you need and therefore how many sheep . That tells you how much land you need for the sheep .
A couple of cows for milk and meat from the calves reared to suit your needs again , means 4 or 5 acres , but you could get away with a few sheep within that area as well. You can then either learn to tan the cow hides and the sheep skins for your own use , or get them done elsewhere.
If you really want to be self reliant then you also need to grow your own sheep and cattle feed . Not difficult at all , it just takes space. An acre will give between say 1 and 2 tons of grain , thats 2240lb - 4480 lbs of feed per year . You can also keep them on just grass alone , but you have to avoid the continental types if you want to do that . Welsh blacks , or dairy shorthorn or many other types will grow well on nothing but grass , and hay in winter. Out of what grain you grew you could feed a good flock of chickens that would supply meat and eggs , for yourself and to sell /barter .
wheat for your bread would also come into this section , 1 sq yard giving up to 1lb of grain approx.
You also get the straw from the wheat , oats , barley and rye , which can be used for bedding , feed , and to make hats , baskets etc to sell and for your own use.
Then if you really want to be self reliant , you can grow linseed for oil ( to preserve wood and make paint , even lino ) and the fibre ,flax, to spin and weave to make your own linen.
Next you can grow hemp , also for oil , and for the fibre to make string , rope and sacking .
Sunflowers can be grown for oil and the waste used as animal feed . The oil can be used for cooking and to run a diesel genny .
Oilseed rape ,canola , the same.
You can even grow cotton in the UK , so you could supply all your own clothing .
You also need to work out how you are going to heat your home . Wood or oil ? oil costs and isn't going to get any cheaper . Wood can be grown for free .. it just takes space. How much space depends on how warm you want to be !!
You can grow all your own oil for fuel , but you would have to buy ( maybe you could club together with others doing the same thing ) a good industrial sized oil press to do this . They are about £3,000 but will press many tons of seed sunflower, rape ,hemp ,linseed etc per day . With one of these machines you get most ( 80% approx) of the oil out of the seed . As a very rough guide approx 1/3 of the weight of the seed is oil , so if you grew 3 ton of seed you get one ton of oil . That equates to 2240lbs of oil and veg oil weighs about 8.5 lb a gallon (very roughly !) , thats about 260 gallons of oil . You also end up with about 2 tons of animal feed from the waste 'cake'. These figures are all rough ...in reallity you would get less , nothing is 100%, but the figures give you a guide to work from .
If you have a tractor or a rotovator , you need fuel to run it . The oil you grow will do this 'if' you get older machinery . But you still need to buy spares and replacements.
If you get horses to work the land , you grow their fuel/feed ie grass and some oats/barley , and they give you manure for the veggie plot . They also provide you with new replacements for free . You can also use oxen to do the work . dairy shorthorn would be fine for this .
You also need to think about water . You need a good supply for yourself and for crops and stock . A clean river/stream will do for stock and crops, but you need springs or a borehole for your own supply.
All these things dictate how much land you 'need' . It just depends on , do you really want to be self sufficient/reliant and to what degree .
So back to the first line really , how long is a ...... lol.
I could go on forever , I very often do .....
cheers Russ