Aspect Ratio Converter
Enter an original size and target ratio to calculate a no-crop canvas and the largest centered crop for the target shape.
Original size
Enter the current canvasResult
Two ways to reach the target ratioKeeps the full image visible by expanding one canvas dimension.
Removes excess area. Whole-pixel rounding can make the output ratio approximate.
What is the difference?
No-crop canvas preserves the complete source at its current scale by expanding one canvas dimension. Centered crop keeps the largest possible area while cutting away excess width or height.
What this aspect ratio converter calculates
This tool compares two ways to place an existing rectangle inside a new aspect ratio. It returns dimensions only; it does not upload, crop, resize or export the original file.
Fit canvas
Keeps the complete source and expands one canvas dimension until the target ratio is reached. The unused area can be filled with a color, blur or design.
Centered crop
Keeps the largest centered area that matches the target ratio and removes excess width or height.
Stretch
Forces the source into a new shape by scaling axes differently. This distorts content, so the calculator does not recommend or calculate it.
How the fit and crop math works
Let the target decimal ratio be r = target width ÷ target height.
fit height = source width ÷ rcrop width = source height × rIf the source is taller than r:
fit width = source height × rcrop height = source width ÷ rResults are rounded to whole pixels because bitmap dimensions cannot contain partial pixels.
Worked example: 16:9 to 4:5
For a 1920 × 1080 source and a 4:5 target, the complete source fits inside a 1920 × 2400 canvas. A centered crop that uses the full original height is 864 × 1080.
The crop keeps 864 of the original 1920 horizontal pixels, so important subjects near the sides would be removed. A real edit may need an off-center crop or a redesigned vertical composition.
After choosing the geometry, scale the result proportionally to the final delivery size, such as 1080 × 1350.
New ratio or fixed export size?
This converter starts with the source size and a target ratio, not a fixed output resolution. It keeps the source at its current scale for the expanded-canvas option. That is why a 1920 × 1080 source needs a 1920 × 2400 canvas to become 4:5 without cropping.
If the final frame must instead be 1080 × 1350, the letterbox and pillarbox calculator scales the source into those fixed bounds and measures the remaining bars. To compare pixels removed or shift the crop toward one edge, use the crop loss calculator. To keep the original ratio and change only resolution, use the missing-dimension calculator.
A reliable conversion workflow
- Inspect the source dimensions with the image checker or enter them directly.
- Choose the target based on the final placement, not the source file.
- Compare the fit canvas and centered crop results.
- Decide what matters more: retaining every source pixel or filling the complete frame.
- Reposition the crop in your editor when the subject is not centered, then export at the required resolution.
Common targets include 1:1 square, 4:5 portrait, 16:9 landscape and 9:16 vertical.
Frequently asked questions
Will the converter modify my image or video?
No. It only calculates geometry. Your source file stays unchanged and is not uploaded.
What is the difference between crop and resize?
Resizing changes pixel dimensions. Cropping removes part of the frame. If source and target ratios differ, resizing alone cannot fill the new shape without distortion.
Why is the fit canvas larger than my source?
The fit result expands one canvas dimension so the full source can sit inside the target shape at its current scale. You may scale the completed canvas down afterward.
Does centered crop always give the best composition?
No. It gives the largest mathematical crop centered in the source. Faces, products or text may require a manually shifted crop.
How can I avoid black bars?
Fill unused canvas space with a designed background, blurred duplicate imagery or other layout elements, or choose a crop that fills the frame.