IMAGE GUIDE
Pixels, DPI and PPI Explained
Pixels, DPI and PPI are often used interchangeably, but they mean different things. Understanding the difference helps you choose the right image size for web, email and print.
Pixels
A pixel is the smallest unit of a digital image. An image that is 1200 × 900 pixels is made up of 1,080,000 individual pixels arranged in a grid. Pixel dimensions determine how much detail the image actually contains.
When you resize an image in QuakeStar, you are changing the number of pixels. Fewer pixels means less detail but also a smaller file.
PPI (pixels per inch)
PPI describes how densely pixels are packed when an image is displayed or printed. It is a relationship between pixel dimensions and physical size.
For example, a 1200 × 900 pixel image displayed at 12 × 9 inches has a PPI of 100. The same image displayed at 4 × 3 inches has a PPI of 300.
Crucially, the PPI value by itself does not change how much detail the image contains. A 1200 × 900 image at 72 PPI and the same image at 300 PPI still have exactly the same pixels.
DPI (dots per inch)
DPI technically refers to printer dots, not image pixels. It describes how many dots of ink a printer lays down per inch. Higher DPI printers can produce smoother output, but the printed result still depends on the pixel data in the image.
Many image editors label the resolution field as "DPI" even when they really mean PPI. In practice, the two terms are often used to mean the same thing: the pixel density of an image.
For digital use, pixels matter most
Websites, email clients and phone screens do not care about DPI or PPI metadata. They display images based on pixel dimensions. A 1200 × 900 image will occupy the same screen space regardless of whether its metadata says 72 PPI or 300 PPI.
This is why QuakeStar's Image Resizer focuses on pixel dimensions rather than DPI. For most digital tasks, the question is "how many pixels wide does this need to be?" not "what is the DPI?"
For print, PPI matters
Print is different. A high-quality print typically needs around 300 PPI at the final printed size. To print a 6 × 4 inch photo at 300 PPI, you need an image that is at least 1800 × 1200 pixels.
If you send a 600 × 400 pixel image to be printed at 6 × 4 inches, the printer will have to stretch the pixels, and the result will look soft or pixelated.
Summary
- Pixels = actual image detail.
- PPI = pixel density for display or print.
- DPI = printer dot density.
- For web and email, focus on pixel dimensions.
- For print, make sure you have enough pixels for the intended size and PPI.