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Start with a pixel count and an image shape

Megapixels to print size

A megapixel count describes area, not a width or height. Add the image’s aspect ratio and your target PPI to estimate both print dimensions.

Enter 0.01–1,000 MP. A rounded camera rating gives an estimate; use the actual image dimensions when you have them.

Width : height, in that order. For portrait, use 2:3 instead of 3:2 or choose Rotate ratio. Each ratio value can be 1–10,000.

300 PPI is an editable starting value, not a promise of quality. Use your print provider’s image-resolution requirement; supported range: 1–10,000 PPI.

Why megapixels alone are not enough

One megapixel is one million pixels of image area. Two images can contain the same total number of pixels while having different shapes. A square 24 MP image has equal edges of about 4,899 pixels; a 24 MP image with a 3:2 ratio has edges of 6,000 and 4,000 pixels. At the same PPI, their print areas match but their widths and heights differ.

If you know the actual file dimensions, the pixels-to-inches converter avoids this estimation step. If you already have a print size in mind, the image PPI calculator checks its resolution from those actual pixels.

The calculation, step by step

Let A be megapixels × 1,000,000 and r be ratio width ÷ ratio height. A rectangle satisfies width × height = A and width ÷ height = r. Solving the two equations gives:

Pixel width = √(A × r)
Pixel height = √(A ÷ r)
Print inches = pixel edge ÷ PPI

Multiply inches by 2.54 for centimeters or 25.4 for millimeters. The calculator keeps unrounded edges for print dimensions, then shows a separate nearest-whole-pixel reference grid. Rounding each edge can slightly change the displayed total megapixels. It does not identify the exact dimensions used by a particular camera.

Worked example: 24 MP at 3:2

24,000,000 × 1.5 = 36,000,000; its square root is 6,000. The other edge is √(24,000,000 ÷ 1.5) = 4,000 pixels. At 300 PPI, divide each edge by 300 to get 20 × 13.333 inches, or approximately 50.8 × 33.867 cm. At 240 PPI, the same pixel count corresponds to 25 × 16.667 inches.

Rotate the ratio to 2:3 and the dimensions exchange places. A different example, 12 MP at 4:3, gives 4,000 × 3,000 pixels and 13.333 × 10 inches at 300 PPI. These are mathematical examples, not camera specifications.

Twice the megapixels does not mean twice the width

At an unchanged ratio and PPI, a linear edge grows with the square root of the pixel count. Doubling 24 MP to 48 MP increases both edges by √2, about 1.414 times. To double both width and height, the pixel area must increase fourfold: 24 MP becomes 96 MP. This is why large changes in a camera’s advertised count can mean smaller changes in print dimensions.

Use the exported image for a final print decision

A crop, reduced-size export or different capture mode can produce fewer pixels than a camera’s nominal rating. A different crop ratio also changes the shape. Enter the count and ratio of the image you intend to print, or switch to its actual pixel edges when they are available. Megapixels are not megabytes; compressed file size is not an input to this calculation.

Adobe’s printed-resolution explanation distinguishes pixel dimensions from how densely those pixels are placed on paper. Changing PPI alone changes physical size; resampling changes the pixel count. Printer ink-dot DPI is a different quantity from image PPI.

The estimates do not rate sharpness or establish a maximum acceptable print. Focus, motion, processing, paper and viewing conditions also matter. Confirm the finished file and your provider’s requirements. For a blank document rather than a photograph, use the paper-size and margin calculator.

A quick estimate with its assumptions visible

This free tool keeps the megapixel count, shape and PPI beside the result so you can revisit a print idea without guessing what went into it. Calculations stay in your browser; no image is uploaded and no entries are stored. Reviewed September 18, 2026. Send corrections to contact@pixelstoinches.org.