Add the actual costs
A road needs one wood and one brick. A settlement adds one sheep and one wheat to that pair. A city upgrade costs three ore and two wheat. A development-card purchase costs one ore, one wheat and one sheep. Enter planned additions, not the buildings already on the board.
Two roads and a settlement
The starting example costs three wood, three brick, one sheep and one wheat: eight cards in total. Owning two wood and one brick leaves a shortage of one wood, two brick, one sheep and one wheat. Extra ore does not automatically cover that shortage; use a legal player trade or a bank/port exchange first.
A shopping list is not a legal move sequence
The totals do not check connectivity, distance rules, building supply already used, bank shortages or turn timing. A city requires an existing settlement; do not add another settlement purchase unless you actually need to build it first. Road Building can provide roads without these resource costs, but it still requires legal placements and available pieces. Remove any free roads from the paid-road count yourself.
Rules, assumptions & further reading
Check the official CATAN rulebooks and Colonist’s base-game rules for the rules at your table. These calculations and worked examples are original mathematical models, not measured win rates. They do not read a live game or establish that a move is legal.