Image Resize Calculator
Calculate new image dimensions while preserving aspect ratio. Estimate file size change after resizing. Common social media presets included.
Common image size presets
| Platform | Size (px) | Aspect Ratio | Notes |
|---|---|---|---|
| YouTube Thumbnail | 1280 × 720 | 16:9 | Minimum. Ideal is 1920×1080 |
| Instagram Square | 1080 × 1080 | 1:1 | Best for grid posts |
| Instagram Portrait | 1080 × 1350 | 4:5 | Maximum recommended portrait |
| Instagram Story | 1080 × 1920 | 9:16 | Full screen vertical |
| Facebook Cover | 820 × 312 | ~2.6:1 | Desktop display |
| WhatsApp DP | 500 × 500 | 1:1 | Circle crop in chat |
| Passport Photo (India) | 413 × 531 | 35×45mm at 300 DPI | White background required |
| Twitter/X Header | 1500 × 500 | 3:1 | Profile page banner |
Frequently asked questions
How is file size after resize estimated?
File size is roughly proportional to the number of pixels (width × height). If you resize from 4000×3000 to 1280×720, the pixel area drops by ~92%. The estimated file size scales by the same ratio. Actual size also depends on content complexity and compression.
Does resizing to smaller dimensions reduce quality?
Downscaling (making smaller) is safe and generally produces clean results. Upscaling (making larger) introduces blurriness because pixels are interpolated — the original detail is not there to recover.
What is a passport photo size in pixels?
A standard Indian passport photo is 35mm × 45mm. At 300 DPI (dots per inch, the print standard), this equals 413 × 531 pixels. The Passport Photo preset is set to these exact dimensions.
How does the Fit in Box option work?
The "Fit in Box" mode scales the image so that its largest dimension (width or height) equals the value you enter, while the other dimension is calculated to preserve the aspect ratio. For example, fitting 4000×3000 in a 1000px box gives 1000×750.
What is the difference between PPI and DPI?
PPI (pixels per inch) is a screen measure — how many pixels fit in one inch of display. DPI (dots per inch) is a print measure — how many ink dots per inch. For digital images, they are used interchangeably. 300 DPI is the standard for print quality.