diff --git a/src/shared/styles/theme.css b/src/shared/styles/theme.css
index 7cee16b..1ce1b34 100644
--- a/src/shared/styles/theme.css
+++ b/src/shared/styles/theme.css
@@ -213,7 +213,10 @@
     font-size: var(--text-3xl);
   }
   h3 {
-    font-size: var(--text-2xl);
+    /* 5vw is tuned to stay under the nav h1 across the whole range: it only
+     * reaches the nav's 32px exactly at the 640px breakpoint where the nav
+     * itself steps up, so h3 never overtakes it. */
+    font-size: clamp(1.5rem, 5vw, var(--text-2xl));
   }
   h4 {
     font-size: var(--text-xl);