Compare the extra production, not the final total
A city replaces a settlement. Its economic gain is the additional production over what that settlement already supplied. Comparing the city’s entire output with a new settlement overstates the upgrade’s benefit because you already owned the original production.
A new settlement adds the output of a new corner, along with any new resource access that corner provides. Treat those as separate benefits. One option might add more expected cards, while the other supplies the missing resource that has prevented you from using cards already in your hand.
Worked example: the twelve-pip upgrade
Your settlement touches 6 ore, 5 wheat and 4 sheep: twelve producing outcomes per 36 fair rolls. Upgrading it adds twelve expected cards over 36 unblocked rolls. An available settlement corner touches 9 wood and 10 brick: seven expected cards over the same interval. The city has the larger raw production gain.
But suppose you currently produce no wood or brick. The seven-pip settlement opens two build inputs you were buying from others. That can make it strategically attractive despite its lower total. Add the road cost, the risk of someone taking the corner and the cards currently in your hand before choosing. The figures are illustrative expectations, not a forecast of the next 36 rolls.
Include the route and the resources you are spending
A city costs three ore and two wheat. A settlement costs wood, brick, wheat and sheep; reaching a distant corner can require additional roads. Compare the complete transaction from your current position. A settlement does not cost only four cards when the route is still unbuilt.
Also consider opportunity cost within your own hand. Spending wheat on an upgrade might postpone a development-card plan; spending road materials on a marginal corner might prevent you contesting a better one. There is no single card-price conversion that captures every board. Explain which future option the purchase leaves available.
Timing can outweigh the production comparison
An opponent can take an empty corner; they cannot take the settlement you already own. That asymmetry can make expansion urgent even when a city looks better on paper. Conversely, building roads speculatively toward an unlikely destination can waste the window in which your established production would have compounded.
Near the finish, evaluate the immediate score and award situation rather than assuming another production investment will repay itself. A good early-game purchase can become too slow late in the game. Afterward, review whether you were solving the board’s current problem or following a rule of thumb whose useful moment had passed.
Sources and scope
- CATAN base-game rules and almanac
Official rulebook index. Use the rulebook for your edition; the advice here covers the base game.
- CATAN base-game FAQ
Official clarifications for trading, building, awards and resource production.
- Colonist base-game building and production reference
A second first-party reference for the familiar building costs and settlement/city production.