Where Should You Build Ports? Distance 300 Is the Hinge

Trade income is an S-curve in the distance between ports, and the inflection sits exactly at 300. Distance 200 pays 13,557. Distance 400 pays 91,443 — doubling the distance nearly septuples the income.

So port placement has exactly one principle: as far apart as possible. Far from each other, and pointed at distant countries.

Income by distance

Gold per trade ship:

Port distance	Gold per ship
50	2,541
100	5,185
200	13,557
250	26,182
300	52,500
350	78,818
400	91,443
500	99,815
600	104,991
800	115,000

Broken into segments, it is obvious where the value lives:

Segment	Gain per 100 distance
100 → 200	+8,371
200 → 300	+38,943
300 → 400	+38,943
400 → 500	+8,371
500 → 600	+5,176

Everything happens between 200 and 400. Past 400 the curve flattens hard — going all the way to 600 adds only 15% over 400.

Three practical rules

1. Never build ports side by side. A distance-50 route pays 2,541. A 125,000 port needs fifty ships to pay for itself.

2. Aim for 400. 300 is barely half the maximum; 400 is about 80% of it. Take a safe 400 over a risky 600.

3. Spread your own ports too. Trade ships run between your ports as well. On a long coastline, one at each end beats three clustered together.

The trap — ports and factories share a counter

This catches almost everyone.

Build three ports and your first factory is already priced as the fourth building (1,000,000). It works in the other direction too.

The formula is min(1,000,000, 2ⁿ × 125,000), where n counts ports and factories combined. Expanding ports without a plan makes the switch to a factory economy brutally expensive.

The building cost calculator accounts for the shared counter.

Trade pays your partner too

When a trade ship arrives, both sides get gold. Building a port also funds your neighbor’s growth.

Two consequences:

• Trading with a weak neighbor feeds them. If you are going to eat them anyway, eat them
• Trading with a strong neighbor is how you keep pace. If you cannot beat them, stay attached

Attacking cuts trade for 5 minutes

Any player you exchange attacks with has trade suspended with you for 5 minutes.

If you have leaned on port income, one border skirmish costs more than it looks. A single 90,000 trade ship route, cut for five minutes, is several cities’ worth of gold.

Choosing your fights is your economy. Leave trade partners alone and expand in directions where you have no route.

Warships and shipping lanes

Ports are also the prerequisite for warships.

• Warship patrol range is 100 tiles
• Trade ships caught by an enemy warship are captured
• Transport boats also launch from ports; sinking means total loss of troops aboard

If your trade route crosses an enemy patrol zone, the income may never arrive. When siting a port, look at whose waters the route crosses.

Where ports sit in your build

Stage	Port priority
Early, land still available	Low. Three cities first
Early, island or peninsula	High. Gold is your only growth path
Midgame	Aggressive, if you can secure distance 400
Factory transition	Weigh the shared counter before adding more

More

• Trade ship calculator — income by distance
• Building cost calculator — shared port/factory counter
• All Six Buildings — including factory rail income
• What Happens When You Betray an Alliance? — trade loss versus betrayal gain