diff --git a/web/src/chart-canvas/chart-canvas.mjs b/web/src/chart-canvas/chart-canvas.mjs
index fe6f682..0bae109 100644
--- a/web/src/chart-canvas/chart-canvas.mjs
+++ b/web/src/chart-canvas/chart-canvas.mjs
@@ -50,7 +50,7 @@
 // Baking runs server-side; the client only renders tiles.
 import { PMTilesArchive, registerPmtilesProtocol } from "./pmtiles-source.mjs";
 import { convertDistance, unitSuffix } from "../lib/units.mjs";
-import { zoomForScale } from "../lib/util.mjs"; // shared scale↔zoom (512-tile MapLibre resolution)
+import { zoomForScale, DEFAULT_PX_PITCH_MM, clampPxPitch } from "../lib/util.mjs"; // shared scale↔zoom (512-tile MapLibre resolution)
 import * as S52 from "./s52-style.mjs";
 import { SpriteBuilder } from "./sprite-builder.mjs";
 // Chart SOURCE / ARCHIVE management lives in its own stateful collaborator now (the
@@ -68,6 +68,12 @@ import {
 import { buildChartLayers, PAT_PREFIX } from "./chart-style.mjs";
 
 const FEATURE_SCALE = 0.01 / 0.35278;
+// The baker emits feature pixel sizes (icon `scale`, `width_px`, `font_size_px`,
+// pattern raster) as if 1 px = 1 typographic point = 0.35278 mm (72 DPI). To render
+// at TRUE physical size we multiply every size by 0.35278/pxPitch (see _scaleSizes
+// in chart-style.mjs / _featureSizeScale below). On the default CSS pixel (0.2645 mm)
+// that is ≈1.333×; a calibrated screen pitch makes it exact.
+const BAKED_FEATURE_PITCH_MM = 0.35278;
 // Linear (constant-velocity) easing for the follow camera — see updateFollow. The
 // default ease-in/out would stall at each fix boundary, reading as a step.
 const LINEAR = (t) => t;
@@ -128,6 +134,7 @@ export class ChartCanvas extends HTMLElement {
     this._sprite = {};
     this._patterns = {};
     this._atlasPpu = 0.08;
+    this._pxPitch = undefined; // calibrated CSS-pixel pitch (mm); undefined → CSS reference. Drives _featureSizeScale.
     this._active = "day";
     this._spriteImg = null;
     this._patternsImg = null;
@@ -178,6 +185,7 @@ export class ChartCanvas extends HTMLElement {
       assets,
       getMap: () => this._map,
       rebuild: () => this._map && this._map.setStyle(this.buildStyle(), { diff: false, validate: false }),
+      getPxPitch: () => this._pxPitch, // SCAMIN gates on the calibrated physical scale (in-place re-gate)
     });
 
     // Shadow DOM: MapLibre CSS must live inside the shadow root, plus a sized
@@ -633,6 +641,23 @@ export class ChartCanvas extends HTMLElement {
     for (const k in osmPaint) setIf("osm", k, osmPaint[k]);
   }
 
+  // Feature-size multiplier that renders baked (point-pixel) sizes at true physical
+  // size on this screen: 0.35278 mm/baked-px ÷ the (calibrated) CSS-pixel pitch. On
+  // the default CSS pixel (0.2645 mm) ≈1.333×; calibration makes it exact.
+  _featureSizeScale() {
+    return BAKED_FEATURE_PITCH_MM / clampPxPitch(this._pxPitch || DEFAULT_PX_PITCH_MM);
+  }
+
+  // Set the calibrated CSS-pixel pitch (mm) and rebuild the style so every feature
+  // size (icons/lines/text/halos/patterns) re-renders at true physical size. Driven
+  // by the shell's screen-calibration setting, mirroring the scale-readout path.
+  setPxPitch(mm) {
+    const v = (typeof mm === "number" && mm > 0) ? mm : undefined;
+    if (v === this._pxPitch) return;
+    this._pxPitch = v;
+    if (this._map && this._sources) this._map.setStyle(this.buildStyle(), { diff: false, validate: false });
+  }
+
   // Switch the basemap live: "coastline" (offline GSHHG land/lakes), "osm"
   // (online OpenStreetMap raster), or "osmvec" (hosted OSM vector .pmtiles).
   // Rebuilds the style from buildStyle() so the basemap sources/layers swap
@@ -1106,12 +1131,17 @@ export class ChartCanvas extends HTMLElement {
     // setScheme/setMariner) keep reading them unchanged.
     const scaminLat = this._sources.scaminLat != null ? this._sources.scaminLat
                       : (this._map ? this._map.getCenter().lat : 0);
+    // True-physical feature sizing: scale the baked (point-pixel) sizes to this
+    // screen. Recompute the pattern raster ratio to match, so AP fills register at
+    // the same physical size when styleimagemissing re-fires after setStyle.
+    const sizeScale = this._featureSizeScale();
+    this._patternPixelRatio = (0.08 / FEATURE_SCALE) / sizeScale;
     const { layers: chartLayers, layerBase, variants, layerVis } = buildChartLayers({
       mariner: this._mariner, palette: this._palette(), atlasPpu: this._atlasPpu, osm: this._osmBasemap(),
       scheme: this._active,
       server: this._sources.server, serverSets: this._sources.sets,
       scaminValues: this._sources.scaminValues, scaminLat, bandsHidden: this._bandsHidden,
-      ignoreScamin: this._ignoreScamin,
+      ignoreScamin: this._ignoreScamin, sizeScale, pxPitch: this._pxPitch,
     });
     this._layerBase = layerBase; this._variants = variants; this._layerVis = layerVis;
 
diff --git a/web/src/chart-canvas/chart-sources.mjs b/web/src/chart-canvas/chart-sources.mjs
index 3df2f54..89a4a93 100644
--- a/web/src/chart-canvas/chart-sources.mjs
+++ b/web/src/chart-canvas/chart-sources.mjs
@@ -15,6 +15,7 @@
 // Where a method used to do `this._map.setStyle(this.buildStyle(), …)` it calls
 // `this.rebuild()`; where it needs the map it calls `this.getMap()`.
 import { PMTilesArchive, MultiArchive } from "./pmtiles-source.mjs";
+import { zoomForScalePhysical } from "../lib/util.mjs";
 
 // NOAA ENC navigational-purpose bands (the rescheming standard) → one vector
 // source each, baked over [min,max] and overzoomed above max (see bake.zig
@@ -71,22 +72,26 @@ export const SCAMIN_BUCKET_LAYERS = new Set(["point_symbols", "soundings", "text
 const SCAMIN_LAT_REBUILD_DEG = 2;
 
 // The display zoom at which a 1:N (scamin) feature first becomes visible at the
-// given latitude: the zoom whose display-scale denominator equals scamin. FRACTIONAL
-// — used directly as a MapLibre layer minzoom, which gives the exact S-52 §8.4
-// cutoff (display scale ≤ SCAMIN ⇒ shown) with no client-side per-zoom computation.
+// given latitude: the zoom whose PHYSICAL display-scale denominator equals scamin.
+// FRACTIONAL — used directly as a MapLibre layer minzoom, which gives the exact
+// S-52 cutoff with no client-side per-zoom computation.
 //
-// SCAMIN is a PRODUCER scale (a real 1:N paper scale), so it is gated against the
-// PHYSICAL display scale — MapLibre's true 512-tile geometry (z0 denom 279541132 =
-// M_PER_PX_Z0_PHYS / OGC_PX_M), NOT the band-pyramid's nominal 256 coordinate. That
-// is exactly half the nominal denom, so the cutoff sits ~1 zoom lower: a 1:59999
-// feature now survives until the screen truly reads ~1:59999 instead of ~1:30000.
-// The deterministic OGC pixel (0.28mm) is used (not the calibratable HUD px-pitch)
-// so this matches the baker's scaminZoom tile floor, which has no screen to measure.
-export function scaminDisplayZoom(scamin, lat) {
+// SCAMIN is "the minimum scale at which the object may be displayed" (S-57 attr
+// 133); S-57 Appendix B.1 §2.2.7 defines it as "the display scale below which the
+// object is no longer displayed", and S-52 6.1.1 defines Display Scale as the TRUE
+// on-glass ratio [distance on display]/[distance on earth]. So we gate against the
+// physical display scale at the (calibrated) screen pixel pitch — the SAME scale the
+// HUD readout and over-scale use — NOT a fixed web/OGC pixel. zoomForScalePhysical is
+// the inverse of that scale, so a SCAMIN 1:N feature vanishes exactly when the screen
+// reads 1:N. pxPitch omitted → the CSS-reference pixel (util default).
+//
+// The baker floors each SCAMIN feature into tiles at floor(scaminZoom) using the
+// deterministic OGC pixel (it has no screen). Real screens are FINER than that pixel,
+// so this client gate lands at/above the baked floor — the tile always carries the
+// feature where we reveal it (gating later than the floor is the safe direction).
+export function scaminDisplayZoom(scamin, lat, pxPitch) {
   if (!scamin) return 0;
-  const denomZ0 = 279541132.0 * Math.cos((lat * Math.PI) / 180);
-  if (denomZ0 <= scamin) return 0;
-  return Math.max(0, Math.min(24, Math.log2(denomZ0 / scamin)));
+  return zoomForScalePhysical(scamin, lat, pxPitch);
 }
 
 // Server sets are baked PER BAND, named "<district>-<band>" (e.g. noaa-d5-general).
@@ -105,10 +110,11 @@ export function bandOfSet(name) {
 }
 
 export class ChartSources {
-  constructor({ assets, getMap, rebuild }) {
+  constructor({ assets, getMap, rebuild, getPxPitch }) {
     this.assets = assets;     // resolved assets base URL (trailing "/")
     this.getMap = getMap;     // () => live MapLibre map (or null)
     this.rebuild = rebuild;   // () => map.setStyle(buildStyle(), {diff:false,validate:false})
+    this.getPxPitch = getPxPitch || (() => undefined); // () => calibrated CSS-pixel pitch (mm); drives SCAMIN gating
     this._ver = 0;            // chart-tile cache-bust token (see refresh)
     this._bands = {};         // band slug → MultiArchive of that band's loaded packs (chart-<slug> source)
     this._scaminValues = [];  // distinct SCAMIN denominators seen in tiles → per-SCAMIN bucket layers
@@ -251,12 +257,13 @@ export class ChartSources {
     const m = this.getMap();
     if (!m) return;
     const lat = m.getCenter().lat;
+    const pitch = this.getPxPitch();
     let style;
     try { style = m.getStyle(); } catch (e) { return; }
     for (const L of (style && style.layers) || []) {
       const hit = /#sm(\d+(?:\.\d+)?)$/.exec(L.id);
       if (!hit) continue;
-      try { m.setLayerZoomRange(L.id, scaminDisplayZoom(+hit[1], lat), L.maxzoom != null ? L.maxzoom : 24); } catch (e) { /* layer removed mid-update */ }
+      try { m.setLayerZoomRange(L.id, scaminDisplayZoom(+hit[1], lat, pitch), L.maxzoom != null ? L.maxzoom : 24); } catch (e) { /* layer removed mid-update */ }
     }
     this._scaminLat = lat;
   }
diff --git a/web/src/chart-canvas/chart-sources.scamin-physical.test.mjs b/web/src/chart-canvas/chart-sources.scamin-physical.test.mjs
new file mode 100644
index 0000000..b817a44
--- /dev/null
+++ b/web/src/chart-canvas/chart-sources.scamin-physical.test.mjs
@@ -0,0 +1,33 @@
+// Verifies SCAMIN gating is on the TRUE physical display scale (S-57 B.1 §2.2.7 /
+// S-52 Display Scale), not a fixed web pixel: a SCAMIN 1:N feature must become
+// visible exactly when the screen reads 1:N — at the (calibrated) pixel pitch.
+// Run: node --test web/src/chart-canvas/chart-sources.scamin-physical.test.mjs
+import test from "node:test";
+import assert from "node:assert/strict";
+import { scaminDisplayZoom } from "./chart-sources.mjs";
+import { scaleDenomPhysical, DEFAULT_PX_PITCH_MM } from "../lib/util.mjs";
+
+test("a SCAMIN 1:N feature's cutoff zoom reads exactly 1:N on the physical scale", () => {
+  const lat = 38.97; // Annapolis
+  for (const scamin of [17999, 21999, 29999, 44999]) {
+    for (const pitch of [DEFAULT_PX_PITCH_MM, 0.254, 0.20]) {
+      const z = scaminDisplayZoom(scamin, lat, pitch);
+      const denomAtCutoff = scaleDenomPhysical(z, lat, pitch);
+      // The displayed scale at the cutoff zoom equals the SCAMIN value (≤0.1% slack).
+      assert.ok(Math.abs(denomAtCutoff - scamin) / scamin < 1e-3,
+        `scamin ${scamin} @ pitch ${pitch}: cutoff reads 1:${Math.round(denomAtCutoff)}`);
+    }
+  }
+});
+
+test("finer pixel pitch pushes the cutoff to a HIGHER zoom (feature hides earlier zooming out)", () => {
+  const lat = 38.97;
+  const coarse = scaminDisplayZoom(17999, lat, 0.2645); // CSS reference
+  const fine = scaminDisplayZoom(17999, lat, 0.20);     // dense screen
+  assert.ok(fine > coarse, `fine pitch ${fine} should exceed coarse ${coarse}`);
+});
+
+test("no pitch arg falls back to the CSS-reference pixel", () => {
+  const lat = 38.97;
+  assert.equal(scaminDisplayZoom(17999, lat), scaminDisplayZoom(17999, lat, DEFAULT_PX_PITCH_MM));
+});
diff --git a/web/src/chart-canvas/chart-style.mjs b/web/src/chart-canvas/chart-style.mjs
index a67f7fe..1ca5e47 100644
--- a/web/src/chart-canvas/chart-style.mjs
+++ b/web/src/chart-canvas/chart-style.mjs
@@ -102,7 +102,30 @@ function textLayers(mariner, palette) {
     },
   }];
 }
-function buildLayers(mariner, palette, atlasPpu, osm) {
+// Multiply every PIXEL-VALUED size property by `k` so S-52 features render at
+// their true physical size on THIS screen. The baker emits sizes (icon `scale`,
+// `width_px`, `font_size_px`) as if 1 CSS px = 1 typographic point (0.35278 mm /
+// 72 DPI); but a CSS px is 1/96 in (0.2645 mm) — and the actual screen may differ
+// again. The element computes k = 0.35278 / pxPitch and passes it in, scaling
+// icons/lines/text/halos together (line-dasharray is in line-width units, so it
+// scales for free). Only sizes are touched — colours/filters/placement are unchanged.
+function _scaleSizes(layers, k) {
+  if (!(k > 0) || Math.abs(k - 1) < 1e-6) return layers;
+  const mul = (v) => (v == null ? v : ["*", k, v]);
+  for (const L of layers) {
+    if (L.layout) {
+      if (L.layout["icon-size"] != null) L.layout["icon-size"] = mul(L.layout["icon-size"]);
+      if (L.layout["text-size"] != null) L.layout["text-size"] = mul(L.layout["text-size"]);
+    }
+    if (L.paint) {
+      if (L.paint["line-width"] != null) L.paint["line-width"] = mul(L.paint["line-width"]);
+      if (L.paint["text-halo-width"] != null) L.paint["text-halo-width"] = mul(L.paint["text-halo-width"]);
+    }
+  }
+  return layers;
+}
+
+function buildLayers(mariner, palette, atlasPpu, osm, sizeScale) {
   // Over an OSM basemap (raster or vector), let its detailed land show through:
   // drop the chart's own land fills so OSM land isn't painted over. Filter by
   // colour token, not class, so it catches LNDARE (LANDA) AND built-up land
@@ -201,7 +224,9 @@ function buildLayers(mariner, palette, atlasPpu, osm) {
   ];
   // Template chart layers (source "chart" is a placeholder rewritten per band
   // by expandChartLayers). Their `filter` is the intrinsic (base) filter.
-  const tmpl = base.concat(complexLineLayers(palette), top, textLayers(mariner, palette));
+  // Scale all pixel sizes to true physical size BEFORE the SCAMIN split so the
+  // *_scamin clones (which share these layout/paint objects) inherit it.
+  const tmpl = _scaleSizes(base.concat(complexLineLayers(palette), top, textLayers(mariner, palette)), sizeScale);
   // SCAMIN AREA/LINE split: each template layer reading one of the four area/line
   // source-layers is IMMEDIATELY FOLLOWED BY a clone reading the matching
   // "<sl>_scamin" source-layer (id "<id>-scamin"). The original now only ever
@@ -324,10 +349,12 @@ export function buildChartLayers({
   server, serverSets, scaminValues, scaminLat, // chart-source state (already resolved)
   bandsHidden,                                 // Set (this._bandsHidden)
   ignoreScamin,                                // DEBUG: drop the per-SCAMIN display gate (show everything in-band)
+  sizeScale = 1,                               // px→true-physical feature-size multiplier (0.35278/pxPitch); see _scaleSizes
+  pxPitch,                                     // calibrated CSS-pixel pitch (mm) → SCAMIN gates on the true physical scale
 }) {
   active = scheme || "day";
   const layerBase = {}, variants = {}, layerVis = {};
-  const tmpl = buildLayers(mariner, palette, atlasPpu, osm);
+  const tmpl = buildLayers(mariner, palette, atlasPpu, osm, sizeScale);
   const out = [];
   // Group each base template layer with the *_scamin clone that _withScamin placed
   // immediately after it (tagged _baseId), so the pair expands TOGETHER per band
@@ -396,13 +423,13 @@ export function buildChartLayers({
           // value). NOT quantized → SCAMIN is still honoured exactly.
           const floor = set.min || 0;
           const lowVals = [], hiVals = [];
-          for (const sc of scaminVals) (scaminDisplayZoom(sc, lat) <= floor + 1e-6 ? lowVals : hiVals).push(sc);
+          for (const sc of scaminVals) (scaminDisplayZoom(sc, lat, pxPitch) <= floor + 1e-6 ? lowVals : hiVals).push(sc);
           const noFilter = lowVals.length
             ? ["any", ["!", ["has", "scamin"]], ["in", ["get", "scamin"], ["literal", lowVals]]]
             : ["!", ["has", "scamin"]];
           mk("#no", and(noFilter), undefined);
           for (const sc of hiVals) {
-            mk("#sm" + sc, and(["==", ["get", "scamin"], sc]), scaminDisplayZoom(sc, lat));
+            mk("#sm" + sc, and(["==", ["get", "scamin"], sc]), scaminDisplayZoom(sc, lat, pxPitch));
           }
         } else {
           mk("", base, undefined);
@@ -467,13 +494,13 @@ export function buildChartLayers({
         // the layer count without quantizing (see the server path for the rationale).
         const floor = dmin || 0;
         const lowVals = [], hiVals = [];
-        for (const sc of scaminValues) (scaminDisplayZoom(sc, lat) <= floor + 1e-6 ? lowVals : hiVals).push(sc);
+        for (const sc of scaminValues) (scaminDisplayZoom(sc, lat, pxPitch) <= floor + 1e-6 ? lowVals : hiVals).push(sc);
         const noFilter = lowVals.length
           ? ["any", ["!", ["has", "scamin"]], ["in", ["get", "scamin"], ["literal", lowVals]]]
           : ["!", ["has", "scamin"]];
         mk("#no", and(noFilter), dmin || undefined);
         for (const sc of hiVals) {
-          mk("#sm" + sc, and(["==", ["get", "scamin"], sc]), scaminDisplayZoom(sc, lat));
+          mk("#sm" + sc, and(["==", ["get", "scamin"], sc]), scaminDisplayZoom(sc, lat, pxPitch));
         }
       } else {
         mk("", base, dmin || undefined);
diff --git a/web/src/chart-canvas/chart-style.sizescale.test.mjs b/web/src/chart-canvas/chart-style.sizescale.test.mjs
new file mode 100644
index 0000000..a8fd090
--- /dev/null
+++ b/web/src/chart-canvas/chart-style.sizescale.test.mjs
@@ -0,0 +1,44 @@
+// Verifies the true-physical feature-size scaling: buildChartLayers({ sizeScale })
+// must multiply every pixel-valued size (icon-size / text-size / line-width /
+// text-halo-width) by sizeScale, and leave them untouched when sizeScale == 1.
+// Run: node --test web/src/chart-canvas/chart-style.sizescale.test.mjs
+import test from "node:test";
+import assert from "node:assert/strict";
+import { buildChartLayers } from "./chart-style.mjs";
+
+function build(sizeScale) {
+  return buildChartLayers({
+    mariner: {}, palette: {}, atlasPpu: 0.08, osm: false, scheme: "day",
+    server: false, serverSets: [], scaminValues: [], scaminLat: 0,
+    bandsHidden: new Set(), ignoreScamin: true, sizeScale,
+  }).layers;
+}
+
+// A size expression wrapped by _scaleSizes looks like ["*", k, <original>].
+function wrappedBy(v, k) {
+  return Array.isArray(v) && v[0] === "*" && v[1] === k;
+}
+
+test("sizeScale wraps icon-size / text-size / line-width / halo with [*, k, …]", () => {
+  const k = 1.3338;
+  const layers = build(k);
+  const lineSolid = layers.find((L) => (L._baseId || L.id || "").startsWith("lines-solid") || L.id?.startsWith("lines-solid@"));
+  const pointSym = layers.find((L) => L.id?.startsWith("point_symbols@"));
+  const text = layers.find((L) => L.id?.startsWith("text@"));
+
+  assert.ok(lineSolid, "a lines-solid variant exists");
+  assert.ok(wrappedBy(lineSolid.paint["line-width"], k), "line-width scaled");
+  assert.ok(pointSym, "a point_symbols variant exists");
+  assert.ok(wrappedBy(pointSym.layout["icon-size"], k), "icon-size scaled");
+  assert.ok(text, "a text variant exists");
+  assert.ok(wrappedBy(text.layout["text-size"], k), "text-size scaled");
+  assert.ok(wrappedBy(text.paint["text-halo-width"], k), "text-halo-width scaled");
+});
+
+test("sizeScale == 1 leaves sizes untouched (no [*, 1, …] wrapper)", () => {
+  const layers = build(1);
+  const lineSolid = layers.find((L) => L.id?.startsWith("lines-solid@"));
+  assert.ok(lineSolid, "a lines-solid variant exists");
+  // Original line-width is ["coalesce", ["get","width_px"], 1] — NOT a "*" wrapper.
+  assert.equal(lineSolid.paint["line-width"][0], "coalesce");
+});
diff --git a/web/src/chartplotter.mjs b/web/src/chartplotter.mjs
index e7fb5a4..47df21c 100644
--- a/web/src/chartplotter.mjs
+++ b/web/src/chartplotter.mjs
@@ -516,6 +516,11 @@ export class ChartPlotter extends HTMLElement {
     // Apply persisted display prefs.
     if (this._scheme !== "day") this._plotter.setScheme(this._scheme);
     this.setAttribute("data-scheme", this._scheme);
+    // Calibrated CSS-pixel pitch drives true-physical feature sizing in the renderer
+    // (the same calibration the scale readout uses). Push it before the first frame.
+    if (typeof this._pxPitch === "number" && this._plotter.setPxPitch) {
+      try { this._plotter.setPxPitch(this._pxPitch); } catch (e) { console.warn(e); }
+    }
     if (Object.keys(this._mariner).length) {
       try { this._plotter.setMariner(this._mariner); } catch (e) { console.warn(e); }
     }
@@ -1699,6 +1704,8 @@ export class ChartPlotter extends HTMLElement {
     try { localStorage.setItem(LS_PX_PITCH, JSON.stringify(this._pxPitch ?? null)); } catch (e) { /* quota/private */ }
     this._persistSettings();
     if (this._hud) this._hud.updateHud();
+    // Re-render features at true physical size for the new pitch (icons/lines/text).
+    if (this._plotter && this._plotter.setPxPitch) { try { this._plotter.setPxPitch(this._pxPitch); } catch (e) { console.warn(e); } }
   }
 
   // Fetch the server-persisted display settings at boot and adopt them over the