diff --git a/lib/dev_config.dart b/lib/dev_config.dart
index 5084fd7..18adfd8 100644
--- a/lib/dev_config.dart
+++ b/lib/dev_config.dart
@@ -3,8 +3,8 @@ import 'package:flutter/material.dart';
 
 /// Developer/build-time configuration for global/non-user-tunable constants.
 
-// Example: Default tile storage estimate (KB per tile), for size estimates
-const double kTileEstimateKb = 25.0;
+// Fallback tile storage estimate (KB per tile), used when no preview tile data is available
+const double kFallbackTileEstimateKb = 25.0;
 
 // Direction cone for map view
 const double kDirectionConeHalfAngle = 30.0; // degrees
diff --git a/lib/widgets/download_area_dialog.dart b/lib/widgets/download_area_dialog.dart
index 59e6b6c..1242483 100644
--- a/lib/widgets/download_area_dialog.dart
+++ b/lib/widgets/download_area_dialog.dart
@@ -62,7 +62,8 @@ class _DownloadAreaDialogState extends State<DownloadAreaDialog> {
     final maxPossibleZoom = _calculateMaxZoomForTileLimit(bounds, minZoom);
     
     final nTiles = computeTileList(bounds, minZoom, maxZoom).length;
-    final totalMb = (nTiles * kTileEstimateKb) / 1024.0;
+    final tileEstimateKb = _getTileEstimateKb();
+    final totalMb = (nTiles * tileEstimateKb) / 1024.0;
     final roundedMb = (totalMb * 10).round() / 10; // Round to nearest tenth
     
     setState(() {
@@ -84,8 +85,22 @@ class _DownloadAreaDialogState extends State<DownloadAreaDialog> {
     }
     return kAbsoluteMaxZoom;
   }
-  
 
+  /// Get tile size estimate in KB, using preview tile data if available, otherwise fallback to constant
+  double _getTileEstimateKb() {
+    final appState = context.read<AppState>();
+    final selectedTileType = appState.selectedTileType;
+    
+    if (selectedTileType?.previewTile != null) {
+      // Use actual preview tile size
+      final previewSizeBytes = selectedTileType!.previewTile!.length;
+      final previewSizeKb = previewSizeBytes / 1024.0;
+      return previewSizeKb;
+    } else {
+      // Fall back to configured estimate
+      return kFallbackTileEstimateKb;
+    }
+  }
 
   @override
   Widget build(BuildContext context) {