Aspect Ratio Calculator
Scale any dimension while keeping the same proportions
Original Dimensions
New Dimensions — Solve For:
Common Aspect Ratio Presets
Common Aspect Ratios Reference
| Ratio | Common Use | Example Resolutions |
|---|---|---|
| 16:9 | HD/4K Video, YouTube, TV | 1280×720, 1920×1080, 3840×2160 |
| 4:3 | Traditional TV, Older Monitors | 800×600, 1024×768, 1600×1200 |
| 1:1 | Instagram Square, Profile Photos | 1080×1080, 500×500 |
| 21:9 | Ultrawide Monitor, Cinema | 2560×1080, 3440×1440 |
| 3:2 | DSLR Camera, 35mm Film | 1080×720, 4500×3000 |
| 9:16 | Instagram/TikTok Stories, Reels | 1080×1920, 720×1280 |
About the Aspect Ratio Calculator
The aspect ratio calculator lets you find a missing image or video dimension while preserving the original proportions. Enter the original width and height plus one new dimension, and the tool instantly computes the other — no math required.
- Solve for either new width or new height from any original dimensions
- One-click presets for 16:9, 4:3, 1:1, 21:9, 9:16, and more
- Shows the simplified ratio (e.g., 1920×1080 → 16:9) alongside the result
- Works with pixels, inches, centimeters, or any consistent unit
- All calculations run in your browser — no data is sent anywhere
How to Use the Aspect Ratio Calculator
- 1
Enter the original dimensions
Type the current width (W1) and height (H1) of your image, video, or design. These can be in any unit — pixels, inches, millimetres — as long as both use the same unit.
- 2
Choose what to solve for
Click Solve for Height (H2) if you know the new width, or Solve for Width (W2) if you know the new height. The selected field is automatically disabled.
- 3
Enter the known new dimension
Type either the new width or new height — whichever one you already have.
- 4
Click Calculate
The result shows the missing dimension, the simplified ratio, and a side-by-side comparison of the original and new sizes.
Tip: Use the preset buttons (16:9, 4:3, 1:1, etc.) to instantly load standard ratios as your original dimensions, then enter any target dimension to get the properly sized output.
Common Use Cases
Video & Streaming
- • Scale a 1920×1080 master to 1280×720 for web delivery
- • Find the correct height for a 16:9 thumbnail given a target width
- • Resize YouTube, Vimeo, or Twitch clips without black bars
Social Media Graphics
- • Convert a landscape photo to a 1:1 square for Instagram
- • Resize a banner to 9:16 for Stories or Reels
- • Scale Twitter/X header images to the correct crop
Web & UI Design
- • Calculate hero image height from a fixed container width
- • Maintain consistent card image ratios across breakpoints
- • Find correct iframe dimensions for embedded videos
Photography & Print
- • Scale a 3:2 DSLR photo to standard print sizes (4×6, 5×7)
- • Check if a crop fits a specific aspect ratio before printing
- • Resize product photos proportionally for e-commerce listings
Game & App Development
- • Generate sprite dimensions for multiple device densities (1x, 2x, 3x)
- • Scale splash screens to different target resolutions
- • Verify texture dimensions stay power-of-two when scaled
Presentations & Slides
- • Resize images to fit a 16:9 slide without distortion
- • Convert older 4:3 slide decks to widescreen format
- • Size embedded video frames proportionally inside slides
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height, written as two numbers separated by a colon (e.g., 16:9). It describes the shape of an image or screen without specifying its exact size — a 1920×1080 frame and an 1280×720 frame both have a 16:9 ratio.
What formula does the calculator use?
To find a missing height: H2 = H1 × W2 ÷ W1. To find a missing width: W2 = W1 × H2 ÷ H1. Both formulas are derived from the fact that the ratio W/H must remain equal between the original and new dimensions.
What is the 16:9 aspect ratio in pixels?
Common 16:9 resolutions are 1280×720 (HD), 1920×1080 (Full HD), 2560×1440 (QHD/2K), and 3840×2160 (4K UHD). Any resolution where width ÷ height ≈ 1.777 is 16:9.
Which aspect ratio should I use for Instagram?
Instagram supports 1:1 (square) for feed posts, 4:5 (portrait, 1080×1350) for the largest in-feed display, and 9:16 (1080×1920) for Stories and Reels. Use the 4:5 preset for the best organic reach in the feed.
Does this calculator work with non-pixel units?
Yes. The calculator only cares about the ratio between width and height, not the actual unit. You can enter dimensions in inches, centimetres, points, or any other unit — the result will be in the same unit you used for input.
Why does the result have decimals?
Not all ratios divide evenly. For example, scaling a 4:3 image to a width of 1920 gives a height of 1440 exactly, but scaling a 16:9 image to 1000px wide gives a height of 562.5. Most image editors round to the nearest whole pixel automatically.
What is the difference between 4:3 and 16:9?
4:3 is nearly square and was the standard for CRT televisions and early computer monitors. 16:9 is wider (about 78% more horizontal space for the same height) and is today's universal standard for HD video, modern monitors, and most web layouts.
Is my data safe? Does this tool send data to a server?
No data leaves your browser. All calculations happen entirely client-side using JavaScript. The numbers you enter are never uploaded or stored anywhere.