Aspect Ratio Calculator — Resize Without Distortion
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.
Original Size
Enter your current dimensions
Aspect Ratio
—
Target Size
Enter one dimension — the other is calculated
Scale Factor
—
What the Aspect Ratio Calculator Does
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.
The Formula
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.
Common Aspect Ratios
| 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 |
Features
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 to Use
No signup, no limits, on any device with a browser.