Image Aspect Ratio & Resize Calculator (Free Online)

Get the correct aspect ratio and exact dimensions for thumbnails, Reels/Shorts, banners, and prints in seconds. This free image aspect ratio calculator converts width × height → ratio, solves missing dimensions from a chosen ratio, and computes Fit (contain) vs Fill (cover) with precise padding or crop math. It also shows megapixels and supports popular presets like 1:1, 4:5, 16:9, 9:16, 3:2, and 2:3.

What this Image Ratio & Resize Tool does

• Simplifies ratios from any pixel size (e.g., 1920×1080 → 16:9).

• Solves missing dimension from a ratio (get height from width or width from height).

• Computes Fit (contain) vs Fill (cover) for any original → target size with padding/crop values.

• Includes popular presets: 1:1, 4:5, 5:4, 3:2, 2:3, 16:9, 9:16.

• Shows megapixels and a scale % option for quick resamples.

• 100% client-side—fast and private.

Perfect for: YouTube thumbnails, Instagram posts/portraits, Reels/TikTok/Shorts covers, Twitter/X headers, Facebook covers, hero banners, blog featured images, and print planning.

How to use the calculator (step-by-step)

1. Enter width & height (or pick a preset ratio).

2. Choose Solve for: “Height from width & ratio” or “Width from height & ratio.”

3. Optional: set a Scale % (e.g., 150% or 50%).

4. For layout planning, open Fit / Fill:

   • Enter Original and Target sizes.

   • Choose Fit (contain) for no cropping (letterboxing/padding shows).

   • Choose Fill (cover) to fill the frame (the tool shows the crop needed).

5. Read the results: Simplified ratio, Solved dimensions, Megapixels, Scaled size, Padding/Crop, and Scale factor.

Fit vs Fill (Contain vs Cover): which should you use?

• Fit (Contain): Keeps the entire image visible inside the target. You may get letterbox bars or need padding to reach the exact size. Ideal for galleries, carousels, and UI where no cropping is allowed.

• Fill (Cover): Scales the image to cover the target completely; extra edges are cropped. Ideal for thumbnails, hero banners, and social covers where filling the frame matters more than preserving the full image.

Tip: For text overlays, design within a central safe area (ample padding) to survive device crops.

Popular sizes & ratios (quick reference)

• YouTube Thumbnail: 1280×720 → 16:9

• Instagram Square: 1080×1080 → 1:1

• Instagram Portrait (Feed): 1080×1350 → 4:5

• Reels / TikTok / Shorts (Vertical): 1080×1920 → 9:16

• Twitter/X Header: 1500×500 → 3:1 (center your subject)

• Facebook Cover: 820×312 (≈ 2.63:1)

Useful examples

Example 1 — Convert pixels to ratio

• Input: 1920×1080 → simplified ratio = 16:9

Example 2 — Solve missing dimension

• You want 4:5 portrait at width 1080 → height = (1080 × 5 / 4) = 1350

Example 3 — Fit vs Fill to target 1080×1920

• Original: 2000×1000 (2:1)

• Fit: Scales until height = 1920 → (2000×? → 1000×? = 1920) → width = 3840, then pad left/right to reach 1080 (letterbox).

• Fill: Scales until width = 1080 → height becomes 540 × scale factor; to cover 1920, it scales much larger and crops top/bottom.
  (The calculator handles the exact math and shows padding/crop values.)

Best practices for crisp, scroll-stopping images

• Start at the native ratio of your target (16:9 for YouTube, 4:5 for IG portrait, 9:16 for Reels).

• Keep text inside a safe box with generous padding.

• For tiny previews (feeds, thumbnails), aim for high contrast and minimal text.

• Resize before exporting to avoid shipping oversized files (speed + SEO).

• Use WebP/AVIF/JPEG appropriately (logos/flat graphics often look best as PNG or lossless WebP).

• If you also print, plan pixels and DPI using a pixels-to-inches calculator.

Troubleshooting & tips

• My image looks soft after resizing → Don’t upscale more than necessary; start from the highest-quality source.

• Text keeps getting clipped on mobile → Use Fit (contain) and place text deeper inside the safe zone; consider platform-specific templates.

• I need exact padding or crop numbers → Use the Fit/Fill panel; it shows the Pad X/Y or Crop X/Y values to replicate in your editor.

• I only know the ratio → Set a custom ratio (e.g., 3:2) and solve for the missing dimension.

FAQs (Image Aspect Ratio & Resize)

Q1. How do I calculate aspect ratio from pixels?
Divide width and height by their greatest common divisor (GCD). Example: 1920×1080 ÷ 120 → 16:9.

Q2. What’s the difference between Fit (contain) and Fill (cover)?
Fit preserves the whole image with padding/letterbox; Fill fills the target and crops excess.

Q3. How do I resize without cropping?
Choose Fit (contain). The tool shows the scaled size plus any padding needed to reach the exact target.

Q4. What ratio is best for YouTube thumbnails?
16:9 at 1280×720 is the standard. Use large text and high contrast.

Q5. What ratio is best for Instagram Reels/TikTok/Shorts?
9:16 (e.g., 1080×1920). Keep text away from bottom UI areas.

Q6. Can I convert 16:9 to 4:5 or 9:16 easily?
Yes—set the target ratio, then use Fill (for full coverage, with crop) or Fit (for no crop, with padding).

Q7. Does the calculator compress my image?
No—it only calculates sizes/ratios. For compression, pair it with an Image Compressor.

Q8. Can I use this for print?
Yes for ratios/dimensions. For print sizing, use a DPI calculator to convert pixels → inches/cm at a chosen DPI.

Q9. Will the tool upload my images?
No. It runs client-side in your browser.

Q10. Can I batch process sizes?
This version is single-image for clarity. If you need batch presets, we can add it.