diff --git a/hdyc-svelte/src/lib/utils/formatConversionValue.js b/hdyc-svelte/src/lib/utils/formatConversionValue.js
new file mode 100644
index 0000000..d2ab1f2
--- /dev/null
+++ b/hdyc-svelte/src/lib/utils/formatConversionValue.js
@@ -0,0 +1,24 @@
+function formatConversionValue(value: number | null | undefined): string {
+  if (value === null || value === undefined || Number.isNaN(value)) {
+    return '—';
+  }
+  if (!Number.isFinite(value)) {
+    return value.toString();
+  }
+  if (value === 0) {
+    return '0';
+  }
+  const rounded = parseFloat(value.toFixed(6));
+  if (rounded !== 0) {
+    return rounded.toString();
+  }
+  const precise = value.toFixed(12).replace(/\.?0+$/, '');
+  if (precise !== '0' && precise !== '') {
+    return precise;
+  }
+
+  // Fallback for extremely small values: use scientific notation but clean it up
+  const scientific = value.toExponential();
+  return scientific.replace(/\.?0+e/, 'e');
+}
+module.exports = { formatConversionValue };
diff --git a/hdyc-svelte/src/lib/utils/formatConversionValue.ts b/hdyc-svelte/src/lib/utils/formatConversionValue.ts
index fb4adbd..2296a8d 100644
--- a/hdyc-svelte/src/lib/utils/formatConversionValue.ts
+++ b/hdyc-svelte/src/lib/utils/formatConversionValue.ts
@@ -13,5 +13,11 @@ export function formatConversionValue(value: number | null | undefined): string
     return rounded.toString();
   }
   const precise = value.toFixed(12).replace(/\.?0+$/, '');
-  return precise || '0';
+  if (precise !== '0' && precise !== '') {
+    return precise;
+  }
+
+  // Fallback for extremely small values: use scientific notation but clean it up
+  const scientific = value.toExponential();
+  return scientific.replace(/\.?0+e/, 'e');
 }