diff --git a/src/components/ScaleSelector.tsx b/src/components/ScaleSelector.tsx
new file mode 100644
index 0000000..758e4a1
--- /dev/null
+++ b/src/components/ScaleSelector.tsx
@@ -0,0 +1,102 @@
+import { Maximize, Check } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover';
+import { useModelStore, SCALE_PRESETS, type ScaleRatio } from '@/stores/useModelStore';
+import { toast } from 'sonner';
+
+interface ScaleSelectorProps {
+  /** "compact" = small icon-style for XR HUD, "default" = labeled button for 2D viewer */
+  variant?: 'default' | 'compact';
+}
+
+export function ScaleSelector({ variant = 'default' }: ScaleSelectorProps) {
+  const { scaleRatio, setScaleRatio, resetFineTuning } = useModelStore();
+
+  const reductions = SCALE_PRESETS.filter(p => p.factor < 1);
+  const enlargements = SCALE_PRESETS.filter(p => p.factor > 1);
+  const oneToOne = SCALE_PRESETS.find(p => p.label === '1:1')!;
+
+  const apply = (r: ScaleRatio) => {
+    setScaleRatio(r);
+    // Reset two-hand scale gesture so it doesn't fight the preset.
+    if (r.label !== '1:1') resetFineTuning();
+    toast.success(`Escala ${r.label}`, {
+      description: 'Medições e ajuste fino mostrados em mm reais.',
+    });
+  };
+
+  const Trigger = variant === 'compact' ? (
+    <Button variant="outline" size="sm" className="h-8 gap-1.5 text-[10px] font-mono" title="Escala do modelo">
+      <Maximize className="h-3.5 w-3.5" />
+      {scaleRatio.label}
+    </Button>
+  ) : (
+    <Button variant={scaleRatio.label !== '1:1' ? 'default' : 'outline'} size="sm" className="gap-2 h-9">
+      <Maximize className="h-3.5 w-3.5" />
+      <span className="font-mono text-xs">Escala {scaleRatio.label}</span>
+    </Button>
+  );
+
+  return (
+    <Popover>
+      <PopoverTrigger asChild>{Trigger}</PopoverTrigger>
+      <PopoverContent className="w-72 space-y-3" side="top" align="start">
+        <div>
+          <p className="font-mono text-[10px] uppercase tracking-widest text-muted-foreground mb-1">
+            Escala atual
+          </p>
+          <p className="font-mono text-sm font-bold text-primary">{scaleRatio.label}</p>
+          <p className="text-[10px] text-muted-foreground mt-1">
+            Medições, ajuste fino e snap são compensados — todos os valores exibidos continuam em mm reais.
+          </p>
+        </div>
+
+        <div>
+          <p className="font-mono text-[10px] uppercase tracking-widest text-muted-foreground mb-1.5">
+            Real
+          </p>
+          <PresetButton current={scaleRatio} preset={oneToOne} onSelect={apply} />
+        </div>
+
+        <div>
+          <p className="font-mono text-[10px] uppercase tracking-widest text-muted-foreground mb-1.5">
+            Reduzir (modelo menor)
+          </p>
+          <div className="grid grid-cols-3 gap-1.5">
+            {reductions.map(p => (
+              <PresetButton key={p.label} current={scaleRatio} preset={p} onSelect={apply} />
+            ))}
+          </div>
+        </div>
+
+        <div>
+          <p className="font-mono text-[10px] uppercase tracking-widest text-muted-foreground mb-1.5">
+            Ampliar (modelo maior)
+          </p>
+          <div className="grid grid-cols-3 gap-1.5">
+            {enlargements.map(p => (
+              <PresetButton key={p.label} current={scaleRatio} preset={p} onSelect={apply} />
+            ))}
+          </div>
+        </div>
+      </PopoverContent>
+    </Popover>
+  );
+}
+
+function PresetButton({
+  preset, current, onSelect,
+}: { preset: ScaleRatio; current: ScaleRatio; onSelect: (r: ScaleRatio) => void }) {
+  const active = preset.label === current.label;
+  return (
+    <Button
+      variant={active ? 'default' : 'outline'}
+      size="sm"
+      className="h-8 font-mono text-[11px] gap-1"
+      onClick={() => onSelect(preset)}
+    >
+      {active && <Check className="h-3 w-3" />}
+      {preset.label}
+    </Button>
+  );
+}