Medieval Castle Cost Calculator

Costs varied enormously by scale. A small Irish tower house could be built for as little as £10, while a modest stone castle like Orford ran around £1,400 in the late 12th century. Larger royal fortresses climbed much higher — Dover Castle cost roughly £7,000, Conwy Castle around £15,000, and the vast concentric fortress at Caernarfon somewhere between £20,000 and £25,000 across its construction. For comparison, Château Gaillard, built at remarkable speed under Richard the Lionheart's personal oversight, cost an estimated £15,000-£20,000 in just two years — a pace that was genuinely unusual for the period.

It was standard for a stone castle to take the better part of a decade to finish, largely because of how labor was actually sourced. Many castles were built substantially using peasant corvée labor — free labor owed to a lord for a limited number of days per year — rather than a continuously available paid workforce, which meant construction could only progress during the specific weeks that labor was actually owed and available, often clustered around gaps in the agricultural calendar.

In principle, more workers means faster construction, and this calculator's model does scale that way directly. In real castle-building projects, though, very large workforces ran into practical limits — coordination difficulties, quarrying and material supply bottlenecks, and diminishing returns from inexperienced conscripted labor all meant that adding more workers didn't always translate into a proportional speedup. Smaller, highly skilled crews were often disproportionately more productive per worker than very large, less experienced ones.

Corvée labor reflects the more common medieval arrangement — peasants owing a limited number of labor-days per year to their lord, meaning a project could only progress during those specific windows, often just a handful of weeks annually. A hired crew reflects a fully paid workforce, like the one Richard the Lionheart used for Château Gaillard outside his own territory, which could work far more of the year continuously — which is a major part of why that castle went up in an unusually fast two years despite its scale.

Comparing medieval and modern currency values is notoriously difficult because the relationship between wages, prices, and purchasing power has changed in ways that don't translate cleanly through simple inflation math. A medieval pound bought a very different basket of goods and services than a modern dollar does, and the relative cost of skilled labor, land, and materials has shifted dramatically over the centuries. Rather than offer a shaky currency conversion, this calculator sticks to the original historical pound figures and lets you compare against real, well-documented castles instead.

A concentric castle design uses multiple nested rings of defensive walls rather than a single keep, dramatically increasing the total stonework, the number of towers and gatehouses needed, and the sheer footprint of the structure. Edward I's Welsh castles, including Caernarfon and Conwy, were built at this grand concentric scale specifically to project royal authority over a newly conquered territory, which is a major reason their costs dwarfed earlier, simpler stone keeps like Orford or Peveril built for more modest local lords.

No — this calculator uses an original model built around real historical castle-cost figures and a commonly referenced rule-of-thumb labor conversion (roughly 20 man-weeks of labor per pound of construction cost), rather than the specific construction rules of any particular tabletop game or video game. It's designed for general worldbuilding and creative planning rather than to match any one system's mechanics exactly.

Yes — the underlying logic (a base cost scaled by size, converted into labor-weeks, then divided by workforce and labor availability) applies to any pre-industrial construction project you're designing, whether it's historically medieval, a fictional fantasy kingdom, or something in between. Just treat the pound figures as your world's equivalent currency and adjust the castle type and scale multiplier to whatever fits your setting.