diff --git a/src/utils/aspectRatioUtils.test.ts b/src/utils/aspectRatioUtils.test.ts
new file mode 100644
index 0000000..6909f3d
--- /dev/null
+++ b/src/utils/aspectRatioUtils.test.ts
@@ -0,0 +1,40 @@
+import { describe, expect, it } from "vitest";
+import { getNativeAspectRatioValue } from "./aspectRatioUtils";
+
+const FALLBACK_RATIO = 16 / 9;
+
+describe("getNativeAspectRatioValue", () => {
+	it("returns the video ratio when no crop region is provided", () => {
+		expect(getNativeAspectRatioValue(1920, 1080)).toBe(16 / 9);
+	});
+
+	it("applies crop width and height to the video ratio", () => {
+		expect(getNativeAspectRatioValue(1920, 1080, { x: 0, y: 0, width: 0.5, height: 1 })).toBe(
+			8 / 9,
+		);
+	});
+
+	it("falls back when video metadata is zero or non-finite", () => {
+		expect(getNativeAspectRatioValue(0, 1080)).toBe(FALLBACK_RATIO);
+		expect(getNativeAspectRatioValue(1920, 0)).toBe(FALLBACK_RATIO);
+		expect(getNativeAspectRatioValue(Number.NaN, 1080)).toBe(FALLBACK_RATIO);
+		expect(getNativeAspectRatioValue(1920, Number.POSITIVE_INFINITY)).toBe(FALLBACK_RATIO);
+	});
+
+	it("falls back when crop dimensions are non-positive or non-finite", () => {
+		expect(getNativeAspectRatioValue(1920, 1080, { x: 0, y: 0, width: 0, height: 1 })).toBe(
+			FALLBACK_RATIO,
+		);
+		expect(getNativeAspectRatioValue(1920, 1080, { x: 0, y: 0, width: 1, height: -1 })).toBe(
+			FALLBACK_RATIO,
+		);
+		expect(
+			getNativeAspectRatioValue(1920, 1080, {
+				x: 0,
+				y: 0,
+				width: Number.POSITIVE_INFINITY,
+				height: 1,
+			}),
+		).toBe(FALLBACK_RATIO);
+	});
+});
diff --git a/src/utils/aspectRatioUtils.ts b/src/utils/aspectRatioUtils.ts
index 887b543..168242b 100644
--- a/src/utils/aspectRatioUtils.ts
+++ b/src/utils/aspectRatioUtils.ts
@@ -11,6 +11,8 @@ export const ASPECT_RATIOS = [
 
 export type AspectRatio = (typeof ASPECT_RATIOS)[number];
 
+const NATIVE_ASPECT_RATIO_FALLBACK = 16 / 9;
+
 /**
  * Returns the numeric value of an aspect ratio.
  * For "native", returns a fallback ratio of 16/9.
@@ -33,7 +35,7 @@ export function getAspectRatioValue(aspectRatio: AspectRatio): number {
 		case "10:16":
 			return 10 / 16;
 		case "native":
-			return 16 / 9;
+			return NATIVE_ASPECT_RATIO_FALLBACK;
 		default: {
 			const _exhaustiveCheck: never = aspectRatio;
 			return _exhaustiveCheck;
@@ -48,7 +50,21 @@ export function getNativeAspectRatioValue(
 ): number {
 	const cropW = cropRegion?.width ?? 1;
 	const cropH = cropRegion?.height ?? 1;
-	return (videoWidth * cropW) / (videoHeight * cropH);
+	if (
+		!Number.isFinite(videoWidth) ||
+		!Number.isFinite(videoHeight) ||
+		!Number.isFinite(cropW) ||
+		!Number.isFinite(cropH) ||
+		videoWidth <= 0 ||
+		videoHeight <= 0 ||
+		cropW <= 0 ||
+		cropH <= 0
+	) {
+		return NATIVE_ASPECT_RATIO_FALLBACK;
+	}
+
+	const ratio = (videoWidth * cropW) / (videoHeight * cropH);
+	return Number.isFinite(ratio) && ratio > 0 ? ratio : NATIVE_ASPECT_RATIO_FALLBACK;
 }
 
 export function getAspectRatioDimensions(
@@ -72,6 +88,6 @@ export function isPortraitAspectRatio(aspectRatio: AspectRatio): boolean {
 }
 
 export function formatAspectRatioForCSS(aspectRatio: AspectRatio, nativeRatio?: number): string {
-	if (aspectRatio === "native") return String(nativeRatio ?? 16 / 9);
+	if (aspectRatio === "native") return String(nativeRatio ?? NATIVE_ASPECT_RATIO_FALLBACK);
 	return aspectRatio.replace(":", "/");
 }