Design tool
Aspect Ratio Calculator
Work out the simplified ratio of any dimensions, or lock a ratio and solve for the missing side. Presets cover 16:9, 4:3, 1:1, 9:16, 21:9 and 3:2, so resizing never distorts what you are resizing.
Find the ratio from pixel dimensions
Simplified ratio
Decimal ratio
Dimensions
Shape preview
Common ratios at a glance
Pick any ratio to load it as a preset in ratio to dimension mode.
Four steps
How to calculate an aspect ratio
- 1
Enter what you know
Type the original width and height, or pick a ratio preset.
- 2
Read the simplified ratio
The calculator reduces the dimensions using their greatest common divisor.
- 3
Solve the missing side
Change one dimension and the other updates to preserve the ratio.
- 4
Use the result
Apply the dimensions in your editor, export settings or CSS.
Common ratios and where they come from
| Ratio | Decimal | Used for |
|---|---|---|
| 16:9 | 1.778 | HD/4K video, most monitors, YouTube |
| 4:3 | 1.333 | Older displays, iPads, many projectors |
| 1:1 | 1.000 | Square social posts, profile images |
| 9:16 | 0.563 | Stories, Reels, TikTok, phone-first video |
| 21:9 | 2.333 | Ultrawide monitors, cinematic video |
| 3:2 | 1.500 | DSLR and mirrorless cameras, 6×4 prints |
| √2:1 | 1.414 | ISO paper, A4, A3, A5 |
That last one is worth understanding: ISO paper uses √2 because it is the only ratio that stays constant when you fold the sheet in half. A4 folded gives A5 with identical proportions, which is why scaling between paper sizes never distorts a layout.
Standard resolutions at each ratio
- 16:9: 1280×720, 1920×1080, 2560×1440, 3840×2160
- 4:3: 640×480, 1024×768, 1600×1200, 2048×1536
- 1:1: 500×500, 1080×1080, 2048×2048
- 9:16: 720×1280, 1080×1920
- 21:9: 2560×1080, 3440×1440
Fitting one ratio into another
Whenever source and destination ratios differ, something has to give. There are three options and each costs something:
- Letterbox: keep the whole frame, add bars. Nothing is lost but the subject gets smaller.
- Crop: fill the frame, cut the edges. Looks better, loses content. Check where faces and text sit before cropping.
- Stretch: never do this. It is instantly visible and looks amateurish.
The calculator tells you the exact overlap. Fitting 16:9 into 1:1 by cropping loses 44% of the width, worth knowing before you discover a logo has been sliced in half.
Related tools
The pixel ruler measures actual dimensions in a screenshot, the unit converter translates pixels to physical units for print, and the percentage calculator handles proportional scaling in percentage terms.
Answers