City Technical Stuff

Variables come in three varieties:
Specific variables relate to individual countries and cities. Thus LAND specifies the land area of your country.
Relative variables are measured against an arbitrary standard. Thus for CLIM the standard is the English climate.
Fudge variables attempt to adjust results to fit with known historical facts. FARMFUDGE, for example, is used to set FARMDENS to reflect England's maximum population in medieval times being about 5 million.

'Population' takes the variables entered and suggests a population. The 10^(LOG(LAND+COAST))^0.666 expression causes population to increase not in simple proportion to Area, as explained elsewhere.
FOOD attempts to estimate if enough food is available by comparing land available with land needed for farming (plus a correction for fishing). In reality 'market forces' will take effect to pull FOOD back towards 100%.
Below the Land Use section is IMPORT%, which allows food to be shipped in to cities. It does not provide extra food for peasants! It's main affect is to reduce the number of city people needing food (at CITYFEED).
WAGON is used in Warning box #2.

MDENS normally shows the density of population around the cities. However if there are no cities (at TLs 0 and 1) it changes to avoid a 'divide by zero' error. RURDENSITY is the density of the whole non-urban population.
FARMDENS is the theoretical maximum that can be supported, using FARMFUDGE to bring it to a realworld level.
WILDENS is, like RURDENS, obtained by subtraction as the density of people living beyond the cities and not providing food for them.
LANDNEEDED considers how much land peasants would need if they were all working hard. If this exceeds the actual land available, then the result is unemployment and food shortages.
MARGIN in the Tech Table sets the amount of surplus food each farmer has left over after feeding his family. This he can sell to city dwellers in exchange for manufactured goods and services. Thus MARGIN=0.1 is a 10% surplus.
WLANDUSE and CLANDUSE are worth watching, representing the land used beyond and around cities respectively.
Knowing the urban population we can calculate the land area needed for farmland to feed the cities. This is FARMAREA.
'City Area' is calculated from the EXP(K+(AR/9)*LN(POP/CCOUNT)) formula. As cities grow so the population density in the centre also grows (skyscrapers), but this is offset by factories and offices, the AR factor. The best way of understanding how this formula works is to play around with it.
To find the number of cities in a country, we start with the assumption that for each Big City there will be six small ones about one tenth the size, for each of these six smaller at one hundredth the size, and so on (this is not a Rule, if you want subsequently to stick say two 2,000 towns together to make a 4,000 one feel free). So the total urban population is going to be the Sum of a progression something like (P) + 6*(P/10) + 6*6*(P/100)...
The CityFudge Data Table takes account of how many terms we want in the progression, and unneeded terms are factored out (for mathmaticians the Factor to Infinity is 2.5).
CITAREA, the land occupied by cities formula, takes ARs from the table to the right and applies them to each city size. As you will be aware from trying out a single city changing ARs affects CITAREA a lot - you are deciding how much space factories and offices will take up.

Military results have a random factor, and you will note that land locked countries can't have ships.

The spreadsheet is calibrated around TL3, so you are strongly advised to leave TL3 values alone in the Tech Table, which is why they are protected. If you want to make changes to TL3, make them elsewhere. The other Tech Levels will be relative to TL3 and are open to debate.

Warnings

(1) URBAN TOO HIGH. There are not enough farmers to feed the cities.
(2) CITY FOOD SHORTAGES? Food can only be transported over short distances by wagon.
(3) FOOD SHORTAGE. Not famine yet, but prices are rising.
(4) URBAN OVERPOPULATION. There is no room left for cities and their associated farming land.
(5) RURAL OVERPOPULATION. There are more peasants than the land can support.
(6) RURAL FOOD SHORTAGES? Not enough land.
(7) FARMLAND TOO HIGH. There cannot be more than 100% Arable land.
(8) NOT POSSIBLE. There cannot be more than 100% useable land.