diff --git a/src/utils/nodeDimensions.ts b/src/utils/nodeDimensions.ts
new file mode 100644
index 00000000..c397a161
--- /dev/null
+++ b/src/utils/nodeDimensions.ts
@@ -0,0 +1,122 @@
+/**
+ * Utility functions for calculating node dimensions based on output aspect ratio.
+ */
+
+/**
+ * Extract dimensions from a base64 data URL image.
+ * @param base64DataUrl - The image as a base64 data URL (e.g., "data:image/png;base64,...")
+ * @returns Promise resolving to {width, height} or null if extraction fails
+ */
+export function getImageDimensions(
+  base64DataUrl: string
+): Promise<{ width: number; height: number } | null> {
+  return new Promise((resolve) => {
+    if (!base64DataUrl || !base64DataUrl.startsWith("data:image")) {
+      resolve(null);
+      return;
+    }
+
+    const img = new Image();
+    img.onload = () => {
+      resolve({ width: img.naturalWidth, height: img.naturalHeight });
+    };
+    img.onerror = () => {
+      resolve(null);
+    };
+    img.src = base64DataUrl;
+  });
+}
+
+/**
+ * Extract dimensions from a video data URL or blob URL.
+ * @param videoUrl - The video as a data URL or blob URL
+ * @returns Promise resolving to {width, height} or null if extraction fails
+ */
+export function getVideoDimensions(
+  videoUrl: string
+): Promise<{ width: number; height: number } | null> {
+  return new Promise((resolve) => {
+    if (!videoUrl) {
+      resolve(null);
+      return;
+    }
+
+    const video = document.createElement("video");
+    video.onloadedmetadata = () => {
+      resolve({ width: video.videoWidth, height: video.videoHeight });
+    };
+    video.onerror = () => {
+      resolve(null);
+    };
+    video.src = videoUrl;
+  });
+}
+
+// Node sizing constraints
+const MIN_WIDTH = 200;
+const MAX_WIDTH = 500;
+const MIN_HEIGHT = 200;
+const MAX_HEIGHT = 600;
+
+// Node chrome: header (~40px), controls/padding (~60px)
+const NODE_CHROME_HEIGHT = 100;
+
+/**
+ * Calculate node dimensions that maintain aspect ratio within constraints.
+ * @param aspectRatio - Width divided by height (e.g., 16/9 for landscape, 9/16 for portrait)
+ * @param baseWidth - Starting width to calculate from (default 300px)
+ * @returns {width, height} dimensions that fit within constraints
+ */
+export function calculateNodeSize(
+  aspectRatio: number,
+  baseWidth: number = 300
+): { width: number; height: number } {
+  // Handle invalid aspect ratios
+  if (!aspectRatio || aspectRatio <= 0 || !isFinite(aspectRatio)) {
+    return { width: 300, height: 300 }; // Return default square
+  }
+
+  // Start with base width and calculate content height
+  let width = Math.max(MIN_WIDTH, Math.min(MAX_WIDTH, baseWidth));
+
+  // Calculate content area height based on aspect ratio
+  // Content height = width / aspectRatio
+  let contentHeight = width / aspectRatio;
+  let totalHeight = contentHeight + NODE_CHROME_HEIGHT;
+
+  // Check if height exceeds max - if so, scale down width to fit
+  if (totalHeight > MAX_HEIGHT) {
+    contentHeight = MAX_HEIGHT - NODE_CHROME_HEIGHT;
+    width = contentHeight * aspectRatio;
+    totalHeight = MAX_HEIGHT;
+  }
+
+  // Check if height is below min - if so, scale up width to fit
+  if (totalHeight < MIN_HEIGHT) {
+    contentHeight = MIN_HEIGHT - NODE_CHROME_HEIGHT;
+    width = contentHeight * aspectRatio;
+    totalHeight = MIN_HEIGHT;
+  }
+
+  // Clamp width to constraints
+  if (width > MAX_WIDTH) {
+    width = MAX_WIDTH;
+    contentHeight = width / aspectRatio;
+    totalHeight = contentHeight + NODE_CHROME_HEIGHT;
+    // Re-clamp height
+    totalHeight = Math.max(MIN_HEIGHT, Math.min(MAX_HEIGHT, totalHeight));
+  }
+
+  if (width < MIN_WIDTH) {
+    width = MIN_WIDTH;
+    contentHeight = width / aspectRatio;
+    totalHeight = contentHeight + NODE_CHROME_HEIGHT;
+    // Re-clamp height
+    totalHeight = Math.max(MIN_HEIGHT, Math.min(MAX_HEIGHT, totalHeight));
+  }
+
+  return {
+    width: Math.round(width),
+    height: Math.round(totalHeight),
+  };
+}