What Is a Pixel? Definition and Explanation

A digital pixel (derived from Picture Element) is the smallest individual data point in a digital raster image. It corresponds to a tiny "dot" that stores a specific color or brightness value. Pixels form the basis of all digital images – from cameras and scanners to monitors and projectors. The more pixels an image contains on a given surface area, the higher the resolution and level of detail.

Properties of a Digital Pixel

• Position in the Grid: Each pixel has a fixed position within the two-dimensional image grid – similar to a cell in a table – defined by row and column.
• Color Information: A pixel stores a color (in color images usually based on the RGB color model). Each color channel – red, green, and blue – receives a value between 0 and 255 (e.g., pure red = R:255, G:0, B:0). Other models like CMYK (for printing) or grayscale are also common.
• No Fixed Physical Size: A digital pixel has no actual size in mm or inches. Only through the pixel density of an output device (see PPI) or specifications like DPI in print does it gain physical dimensions.
• Resolution: The total number of pixels (width × height, e.g., 1920 × 1080) determines the image resolution.
• No Metadata: A pixel contains only color or brightness information. Additional image data such as capture date, camera model, or GPS coordinates are stored separately (e.g., as EXIF data in JPEG files).

Pixel Count and Image Resolution

The resolution of a digital image is defined by the number of pixels in width and height (e.g., 1920 × 1080 pixels). The more pixels, the higher the level of detail. The following image illustrates the impact of pixel count on image sharpness:

Formula - File Size Calculation

Using the resolution (pixel width and height), the theoretical (uncompressed) file size in bytes is calculated.

File Size = Pixel(x) × Pixel(y) × 24 Bit8

Example: An image with a resolution of 1920 × 1080 pixels and 24-bit color depth (8 bits per RGB channel) results in:

File Size = 1920(Pixel) × 1080(Pixel) × 24 Bit8 = 5.93 MB    Detailed calculation in the Pixel Calculator

Color Depth of a Pixel

The color depth of a pixel determines how many different color values can be displayed. It is specified in bits per channel or bits per pixel:

• 8 Bits per Color Channel (24 Bits Total): Standard for JPEG, PNG, and most displays. Each of the three RGB channels gets 256 values, resulting in approx. 16.7 million colors.
• More than 8 Bits (e.g., 10, 12, or 16 Bits): Also known as "Deep Color". Used in professional image editing, HDR content, and medical imaging. Enables smoother gradients and avoids visible banding.

The following graphic illustrates the difference in color depth:

Memory Requirement of a Pixel

A pixel with 24-bit color depth requires 3 bytes of memory (uncompressed). An image with 1920 × 1080 pixels therefore takes up about 6.2 MB:

1920 × 1080 × 3 bytes = 6,220,800 bytes (≈ 5.93 MB)

Compressed image formats such as JPEG or PNG reduce this memory requirement – lossless or lossy, depending on the method.

Digital vs. Physical Pixel

A digital pixel is an abstract data value in a file – without a fixed size. A physical pixel is a real light-emitting unit on a display (e.g., LCD or OLED). The size and arrangement of physical pixels determine the PPI and thus the image sharpness.

Subpixels on Screens

Physical pixels usually consist of three subpixels – red, green, and blue. These emit light and form visible colors through additive color mixing. The exact layout (e.g., RGB stripe, PenTile matrix) affects sharpness, color rendering, and efficiency.

The subpixel structure varies depending on display type and can be seen under a microscope or extreme magnification.