Plain-language reference
Print & Pixel Glossary
Short definitions for the measurements and decisions you meet in our calculators. Follow the related guides for worked examples.
- Pixel
- One sample in a raster image’s grid. The number of pixels across and down describes its dimensions; a pixel has no single physical size until the image is placed at a specified density.
- PPI · pixels per inch
- The number of image pixels occupying one inch of a placed image. Divide pixels by PPI to find inches. A display’s PPI instead describes its native grid over the viewable physical panel.
- DPI · dots per inch
- The dot density of a printer’s marking process. It is distinct from the image PPI supplied to the printer; do not use an advertised printer DPI as your image-density target without appropriate guidance.
- Pixel dimensions
- The width and height of a raster file, such as 2400 × 3000 pixels. These numbers describe spatial samples, not the file’s compressed size in bytes.
- Megapixel
- One million pixels. Multiply width by height and divide by 1,000,000. A 4000 × 3000 file has 12 megapixels, regardless of its intended physical print size.
- Effective PPI
- The density resulting from the actual placement size and crop. A 3000-pixel edge spread over 10 inches has an effective density of 300 PPI, whatever resolution label is stored in the file.
- Aspect ratio
- Width relative to height, expressed as a proportion. A 2400 × 3000 image reduces to 4:5. Reversing it to 5:4 changes orientation.
- Orientation
- Whether width and height describe a portrait, landscape or square arrangement. Use the decoded image orientation when metadata rotates a stored pixel grid.
- Resizing
- Changing dimensions. In a raster editor this may involve resampling; changing only physical size metadata can keep the original pixel dimensions. State which dimensions are changing.
- Resampling
- Creating a new pixel grid from an existing image. Adding samples increases pixel dimensions but does not by itself establish newly captured detail or improved visual quality.
- Crop
- Removing image area to change composition or shape. Unlike a proportional resize, it changes which parts of the original remain visible.
- Fit
- Uniformly scaling the complete image inside a target rectangle. Different ratios leave unused space on two edges. The full image is retained.
- Fill
- Uniformly scaling an image to cover a target rectangle. Different ratios crop some of the image. This preserves shape, unlike stretching each axis independently.
- Trim size
- The intended finished dimensions after cutting. They may differ from the full artwork canvas when bleed extends outside the cut boundary.
- Bleed
- Artwork extending beyond the intended trim boundary. Its required amount and file representation come from the print provider, not from a universal default.
- Safe area
- An inset region inside trim for essential text and details. It is separate from outside bleed and should follow the requirements of the specific product.
- Margin
- Space reserved inside a sheet edge. A user-entered margin is a planning choice and does not establish a printer’s actual printable area.
- Pixel rounding
- Converting a fractional pixel dimension to a whole number. Nearest minimizes the per-axis difference; rounding up meets at least the entered target PPI on each axis.
- Print proof
- A test output used to inspect a proposed result. A proof at the intended scale can reveal issues that a smaller, denser full-image test hides.
- CSS pixel
- A browser layout unit. CSS defines 96 CSS pixels per CSS inch. A CSS pixel does not always correspond to one native screen pixel.
- REM
- A CSS length relative to the root font size. For example, 1.5 rem equals 24 CSS pixels at a 16-pixel reference. A changed reference changes the result.
- EM
- A CSS length whose font reference depends on the property: font-size uses the parent reference, while padding generally uses the element’s computed font size.
- Viewport
- The browser area used for layout, measured in CSS pixels. vw and vh use large viewport dimensions; they are not physical panel measurements.
- Pixel pitch
- The physical spacing of display pixels under the rectangular square-pixel model. In millimeters, pitch equals 25.4 divided by screen PPI.