Fief

Its a piece of land given to a person in medeival society to rule on and to raise a small army to help the king of the country. I made a standard for the size of land that is suitable for one such unit. I named it estate or village. 1 estate is a square 1 mil long and 1 mil wide. Note that 1 mil is equal to 2 km. 1 estate is therefore equal to 4 sq km or 1000 acres. It means its enough for growing food for 1000 people traditionally if all of it is arable. Usually only 80% of it would be arable, so 800 people. There can be 16 farmers, each using 40 acres of arable land and leaving 10 acres in form of a forest.

One acre requires 40 hours of farm work right at farm. Other related works take:

5 hours for milking - 156.25 kg @ 31.25 kg/hour
5 hours excretions processing - 800 kg @ 160 kg/hour
2.5 hours taking out vegetable oil from seeds using bulls - 12.5 kg @ 5 kg/hour
2.5 hours cleaning grains
2.5 hours animal care including preparing meal, feeding, taking out
2.5 hours butchering including slaughtering, cutting meat, mincing etc

These extra works are 20 hours. So, a farmer have to work 60 hours per crop per acre. In our calculations its 1 crop per year, so 60 hours per acre per year.

Ideal time for a farmer to work per year is 2400 hours. It make him work at 40 arable acres.

There are 365 days a year. Take out 15 days for gazetted holidays. The remaining 350 days means 50 weeks. Give an off day per week. 300 working days. Give 30 days leave per year for sickness etc. 270 working days a year. If the farmer works 6 hours of actual work (no talking, resting, eating, drinking etc during that) then per year per farmer 1620 hours of work. If work 8 hours a day actual work then 2160 hours a year per farmer. There is 1.25 males of working age in a family of five (explained below). If each worker works 7 hours a day actual work then 2362.5 hours work per family of five per year.

Lets keep work day 6 hours long per worker and 270 working days a year, so per worker 1620 hours of work per year. Lets suppose a woman can work 2 hours a day doing things like milking cow, cleaning grains etc, then its 2160 hours. Lets keep a family's total working hours at 2160 hours a year. To help the prime male worker, either a female work, or a sub-prime male worker works, or the prime male worker himself works the extra 2 hours.

The family still have 40 acres farm to work on. To make this happen we have to cut time spent at each acre, see below:

Actual farming, per acre, 36 hours, not 40 hours, because at 80% of farm the farmer have to grow the crop too and cut it too, so 32 hours for that, for the rest 20% of farm the farmer only have to cut, the crops there grow naturally because its a pond, forest, natural grass land for bulls etc, half effort there, so 4 hours there. 18 hours for other works as animal caring, feeding, food preparation have to be done by farmer in his own time. So, 54 hours per acre, 2160 total hours, 40 acres.

800 arable acres per fief. Keep 200 arable acres for thick forests where people don't go and are reserved for wild life. Keep 200 acres for thin forests, lake and natural grass land where people go to cut trees, to feed war horses and to collect honey. So, 400 arable acres given to farmers, 10 farmers in each fief.

Note that for each person there is a need of 144 hours of work, details are:

54 hours - farming and related works (discussed above)
27 hours - cloth, shoes, dye, herbs etc industry
27 hours - metal, construction, pottery, furniture etc industry
18 hours - commercial services such as trade, hair cutters, dentists etc
18 hours - govt industries such as military, police, judiciary, rulers, spies, record keepers etc

That is approx 25 families per fief. 20% population of empire lives in cities, 80% in villages, so 100 people per fief.