Original Size
Enter your current dimensions
Aspect Ratio
—
Target Size
Enter one dimension — the other is calculated
Scale Factor
—
Enter your original width and height, then one target dimension — the other is calculated to keep the exact same proportions. Free, no signup, runs in your browser.
Enter your current dimensions
Aspect Ratio
—
Enter one dimension — the other is calculated
Scale Factor
—
The Aspect Ratio Calculator keeps an image or video at the same proportions when you change its size. You enter the original width and height, then type one target dimension — the new width or the new height — and it works out the matching value so nothing gets stretched or squished.
It also shows the simplified aspect ratio (like 16:9 or 4:3) and the scale factor between the original and target sizes. That makes it quick to confirm a resize is proportional, or to check what ratio a given set of dimensions actually is.
Everything is calculated instantly in your browser as you type — nothing is uploaded, and there's no signup.
Aspect ratio is just width divided by height, and a proportional resize keeps that ratio constant: W1 ÷ H1 = W2 ÷ H2. From there, if you know the new width, the new height is H2 = H1 × (W2 ÷ W1); if you know the new height, the new width is W2 = W1 × (H2 ÷ H1). The calculator does this for you, but the math is simple enough to sanity-check by hand.
| Ratio | Example Size | Where It's Used |
|---|---|---|
| 16:9 | 1920×1080 | YouTube, TVs, most video |
| 9:16 | 1080×1920 | Reels, TikTok, Stories |
| 1:1 | 1080×1080 | Square social posts |
| 4:3 | 1024×768 | Older displays, some photos |
| 3:2 | 3000×2000 | DSLR photography, prints |
Proportional Resize
Enter one target dimension and get the other automatically.
Simplified Ratio
See the clean ratio like 16:9, not a messy decimal.
Scale Factor
Know exactly how much bigger or smaller the new size is.
Live Results
Values update instantly as you type — no calculate button.
100% Private
All math runs in your browser — nothing is sent anywhere.
Free Forever
No signup, no limits, on any device with a browser.