Image Crop Calculator
Calculate crop dimensions to fit a target aspect ratio while maximizing area.
About this calculator
Fitting an image into a specific aspect ratio without stretching or distorting it means cropping away part of the frame, and this calculator finds the largest possible crop that hits your target ratio exactly. It first compares your source image's own width-to-height ratio against the target ratio: if the source is proportionally wider than the target, the full height is kept and width gets trimmed down to match; if the source is proportionally taller, the full width is kept and height gets trimmed instead. Either way, only one dimension ever needs to shrink, which is what maximizes retained area — trimming both dimensions would throw away more of the image than necessary to hit the same target ratio.
The crop is centered by default, with the offset split evenly on both sides of whichever dimension was reduced, since a symmetric center crop is usually the safest starting point when you don't know in advance where the important subject sits in the frame. Percentage retained tells you how much of the original pixel count survives the crop, which matters directly for print and display resolution — a photo cropped down to 60% of its original area effectively loses that much resolution for its new aspect ratio, which can matter if you're planning to print large or need to preserve fine detail. This calculator only computes the ideal centered crop geometry; it doesn't know where faces, text, or a subject actually sit in your image, so a photo with an off-center subject may need the offset adjusted manually rather than relying on the centered default.
Inputs
Results
Crop Width
4,000 px
How to Use This Calculator
- Enter the Source Width and Source Height in pixels from the original image file.
- Enter the Target Ratio Width and Height (e.g., 16 and 9 for a 16:9 crop).
- Review the Crop Width and Crop Height in pixels for the center-cropped output.
- Check Percentage Retained and Pixels Removed to understand how much of the image is lost.
- Use X Offset and Y Offset to position the crop precisely within your image editing application.
How the result changes with Source Width
| Source Width | Crop Width |
|---|---|
| 2,000 | 2,000 px |
| 3,000 | 3,000 px |
| 6,000 | 5,333 px |
| 10,000 | 5,333 px |
What each input means
- Source Width
- Width of the original image in pixels.
- Source Height
- Height of the original image in pixels.
- Target Ratio Width
- Width component of the target aspect ratio (e.g., 16 for 16:9).
- Target Ratio Height
- Height component of the target aspect ratio (e.g., 9 for 16:9).
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersSource Width = 4000, Source Height = 3000, Target Ratio Width = 16, Target Ratio Height = 9 = 4 input(s) provided
- Calculate Crop Width4000 = 4000
- Calculate Crop Height2250 = 2250
- Calculate Area RetainedArea Retained75 = 75
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does the calculator only ever shrink one dimension instead of both?
Shrinking a single dimension until the ratio between width and height matches the target is always the crop that keeps the most original pixels, since reducing both dimensions to hit the same target ratio would necessarily remove more area than reducing just one. This is a direct consequence of comparing the source and target ratios: whichever dimension is proportionally in excess is the only one that needs to come down.
Why is the crop centered instead of positioned somewhere else in the frame?
Centering the crop symmetrically on the dimension being reduced is a reasonable default when the calculator has no information about where the subject of the photo actually sits — a face near one edge, for example, could get cut off by a purely centered crop. The offset values are provided precisely so you can shift the crop manually in your editing software if the important part of the image isn't centered.
Does a lower percentage retained mean my image will look worse after cropping?
It means fewer of the original pixels survive into the final image, which reduces the effective resolution available for that new aspect ratio — a bigger concern if you're printing large or need to zoom in later than if the image is only going to be viewed at a smaller size on screen. A crop retaining 50% of the original area can still look sharp displayed small, but will show more softness enlarged than the uncropped original would.
Why does cropping a 4:3 photo to 16:9 remove more area than cropping it to 3:2?
The further a target ratio is from the source image's own proportions, the more of one dimension has to be trimmed to reach it — 16:9 is considerably wider relative to height than 4:3 is, so matching it from a 4:3 source requires cutting away a larger share of the vertical dimension than a closer target ratio like 3:2 would.
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