diff --git a/internal/theme/css.go b/internal/theme/css.go
index 7f3c843..c57819a 100644
--- a/internal/theme/css.go
+++ b/internal/theme/css.go
@@ -7,11 +7,12 @@ import (
 
 // FontFile represents a font file for CSS generation
 type FontFile struct {
-	Family string
-	Weight string
-	Style  string
-	URL    string
-	Format string // "woff2", "woff", "truetype"
+	Family       string
+	Weight       string
+	Style        string
+	URL          string
+	Format       string // "woff2", "woff", "truetype"
+	UnicodeRange string // optional; preserves Google's subset splitting for self-hosted fonts
 }
 
 // GenerateCSS generates CSS variable declarations from theme settings
@@ -31,8 +32,11 @@ func GenerateCSS(theme *Theme, googleFontURLs []string, fontFaces []FontFile) st
   font-weight: %s;
   font-style: %s;
   font-display: swap;
-}
 `, ff.Family, ff.URL, ff.Format, ff.Weight, ff.Style)
+		if ff.UnicodeRange != "" {
+			fmt.Fprintf(&css, "  unicode-range: %s;\n", ff.UnicodeRange)
+		}
+		css.WriteString("}\n")
 	}
 
 	if len(googleFontURLs) > 0 || len(fontFaces) > 0 {
@@ -63,6 +67,8 @@ func GenerateCSS(theme *Theme, googleFontURLs []string, fontFaces []FontFile) st
 	// Button class definitions
 	WriteButtonClasses(&css, theme.Buttons)
 
+	writeFontSizeOverrideRules(&css, theme.Typography)
+
 	return css.String()
 }
 
@@ -124,15 +130,65 @@ func writeTypographyVars(css *strings.Builder, typography *ThemeTypography) {
 	writeVar(css, "font-sans", bodyStack)
 	writeVar(css, "font-mono", monoStack)
 
-	// Font size base as rem
-	if typography.FontSizeBase != "" {
-		writeVar(css, "font-size-base", typography.FontSizeBase+"px")
+	if v := NormalizeFontSizeBase(typography.FontSizeBase); v != "" {
+		writeVar(css, "font-size-base", v)
 	}
 	if typography.LineHeightBase != "" {
 		writeVar(css, "line-height-base", typography.LineHeightBase)
 	}
-	// Font weight base
 	writeVar(css, "font-weight-base", getFontWeight(typography.FontWeightBase))
+	for _, k := range FontSizeOverrideKeys() {
+		v := typography.FontSizeOverrides[k]
+		if v == "" || ValidateFontSize(v) != nil {
+			continue
+		}
+		writeVar(css, "fs-"+k, v)
+	}
+}
+
+var fontSizeOverrideSelectors = map[string]string{
+	"h1": "h1", "h2": "h2", "h3": "h3", "h4": "h4", "h5": "h5", "h6": "h6",
+	"nav-link":         ".bn-navbar a",
+	"hero-title":       ".bn-hero-title",
+	"hero-subtitle":    ".bn-hero-subtitle",
+	"index-card-title": ".bn-post-card-title",
+}
+
+var headingOverrideKeys = map[string]bool{"h1": true, "h2": true, "h3": true, "h4": true, "h5": true, "h6": true}
+
+// writeFontSizeOverrideRules emits element rules for overrides that cannot be
+// consumed via var() fallbacks. Headings go in @layer base so Tailwind
+// utilities on blocks still win; chrome rules stay unlayered so they beat the
+// utility classes baked into builtin templates. Emitted last so they win
+// same-specificity cascade inside this sheet.
+func writeFontSizeOverrideRules(css *strings.Builder, typography *ThemeTypography) {
+	if typography == nil || len(typography.FontSizeOverrides) == 0 {
+		return
+	}
+	var headings, chrome []string
+	for _, k := range FontSizeOverrideKeys() {
+		v := typography.FontSizeOverrides[k]
+		sel, ok := fontSizeOverrideSelectors[k]
+		if !ok || v == "" || ValidateFontSize(v) != nil {
+			continue
+		}
+		rule := fmt.Sprintf("%s { font-size: var(--fs-%s); }", sel, k)
+		if headingOverrideKeys[k] {
+			headings = append(headings, "  "+rule)
+		} else {
+			chrome = append(chrome, rule)
+		}
+	}
+	if len(headings) > 0 {
+		css.WriteString("\n@layer base {\n")
+		css.WriteString(strings.Join(headings, "\n"))
+		css.WriteString("\n}\n")
+	}
+	if len(chrome) > 0 {
+		css.WriteString("\n")
+		css.WriteString(strings.Join(chrome, "\n"))
+		css.WriteString("\n")
+	}
 }
 
 func writeSpacingVars(css *strings.Builder, spacing *ThemeSpacing) {
@@ -361,7 +417,7 @@ func WriteButtonClasses(css *strings.Builder, buttons *ThemeButtons) {
   align-items: center;
   justify-content: center;
   padding: 0.5rem 1rem;
-  font-size: 1rem;
+  font-size: var(--fs-button, 1rem);
   font-weight: 500;
   border-radius: var(--button-radius, 0.375rem);
   transition: all 150ms ease;
@@ -370,9 +426,9 @@ func WriteButtonClasses(css *strings.Builder, buttons *ThemeButtons) {
 }
 
 /* Button sizes */
-.btn-sm { padding: 0.375rem 0.75rem; font-size: 0.875rem; }
-.btn-md { padding: 0.5rem 1rem; font-size: 1rem; }
-.btn-lg { padding: 0.75rem 1.5rem; font-size: 1.125rem; }
+.btn-sm { padding: 0.375rem 0.75rem; font-size: calc(var(--fs-button, 1rem) * 0.875); }
+.btn-md { padding: 0.5rem 1rem; font-size: var(--fs-button, 1rem); }
+.btn-lg { padding: 0.75rem 1.5rem; font-size: calc(var(--fs-button, 1rem) * 1.125); }
 
 /* Theme-aware button types */
 .btn-primary {
diff --git a/internal/theme/defaults.go b/internal/theme/defaults.go
index cac7598..2371718 100644
--- a/internal/theme/defaults.go
+++ b/internal/theme/defaults.go
@@ -229,12 +229,13 @@ type ColorScheme struct {
 
 // ThemeTypography represents typography settings
 type ThemeTypography struct {
-	FontHeading    string `json:"fontHeading"`
-	FontBody       string `json:"fontBody"`
-	FontMono       string `json:"fontMono"`
-	FontSizeBase   string `json:"fontSizeBase"`
-	LineHeightBase string `json:"lineHeightBase"`
-	FontWeightBase string `json:"fontWeightBase"`
+	FontHeading       string            `json:"fontHeading"`
+	FontBody          string            `json:"fontBody"`
+	FontMono          string            `json:"fontMono"`
+	FontSizeBase      string            `json:"fontSizeBase"`
+	LineHeightBase    string            `json:"lineHeightBase"`
+	FontWeightBase    string            `json:"fontWeightBase"`
+	FontSizeOverrides map[string]string `json:"fontSizeOverrides,omitempty"`
 }
 
 // ThemeSpacing represents spacing settings
diff --git a/internal/theme/fontsize.go b/internal/theme/fontsize.go
new file mode 100644
index 0000000..f9e71bb
--- /dev/null
+++ b/internal/theme/fontsize.go
@@ -0,0 +1,96 @@
+package theme
+
+import (
+	"fmt"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+var fontSizeOverrideKeys = map[string]bool{
+	"h1": true, "h2": true, "h3": true, "h4": true, "h5": true, "h6": true,
+	"post-title": true, "post-lede": true, "post-body": true,
+	"post-h2": true, "post-h3": true, "post-meta": true,
+	"page-title": true, "page-lede": true, "index-card-title": true,
+	"hero-title": true, "hero-subtitle": true,
+	"button": true, "nav-link": true,
+}
+
+var fontSizePattern = regexp.MustCompile(`^(\d+(?:\.\d+)?|\.\d+)(rem|px)$`)
+
+// FontSizeOverrideKeys returns the canonical override keys, sorted.
+func FontSizeOverrideKeys() []string {
+	keys := make([]string, 0, len(fontSizeOverrideKeys))
+	for k := range fontSizeOverrideKeys {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
+// ValidateFontSize accepts unit-suffixed CSS lengths within sane bounds.
+// Values are emitted into a stylesheet, so this is a security gate.
+func ValidateFontSize(v string) error {
+	m := fontSizePattern.FindStringSubmatch(v)
+	if m == nil {
+		return fmt.Errorf("font size %q must be a number with rem or px unit", v)
+	}
+	n, err := strconv.ParseFloat(m[1], 64)
+	if err != nil {
+		return fmt.Errorf("font size %q is not a number", v)
+	}
+	switch m[2] {
+	case "rem":
+		if n < 0.25 || n > 10 {
+			return fmt.Errorf("font size %q out of range (0.25rem to 10rem)", v)
+		}
+	case "px":
+		if n < 4 || n > 160 {
+			return fmt.Errorf("font size %q out of range (4px to 160px)", v)
+		}
+	}
+	return nil
+}
+
+// NormalizeFontSizeBase upgrades legacy bare px numbers ("16") to "16px" and
+// validates unit-suffixed values. Returns "" for anything invalid so bad
+// stored data degrades to the CSS fallback instead of breaking the sheet.
+func NormalizeFontSizeBase(v string) string {
+	v = strings.TrimSpace(v)
+	if v == "" {
+		return ""
+	}
+	if _, err := strconv.ParseFloat(v, 64); err == nil {
+		v += "px"
+	}
+	if err := ValidateFontSize(v); err != nil {
+		return ""
+	}
+	return v
+}
+
+// SanitizeFontSizeOverrides drops empty values, rejects unknown keys and
+// invalid values, and returns a fresh map safe to persist and emit.
+func SanitizeFontSizeOverrides(m map[string]string) (map[string]string, error) {
+	if len(m) == 0 {
+		return nil, nil
+	}
+	out := make(map[string]string, len(m))
+	for k, v := range m {
+		if v == "" {
+			continue
+		}
+		if !fontSizeOverrideKeys[k] {
+			return nil, fmt.Errorf("unknown font size element %q", k)
+		}
+		if err := ValidateFontSize(v); err != nil {
+			return nil, err
+		}
+		out[k] = v
+	}
+	if len(out) == 0 {
+		return nil, nil
+	}
+	return out, nil
+}