File size, pixels, and DPI

Whether you're an artist showcasing your work, a dropshipper launching a new print-on-demand store, or a creator refining your craft, knowing how these elements interact is crucial to achieving high-quality prints.

Have you ever struggled with blurry or pixelated images in your prints? Or wondered why your carefully crafted design doesn’t look as sharp as expected on a canvas? These challenges are common, but the solution lies in understanding the technical aspects of file preparation.

This guide will walk you through the essentials of file size, pixels, and DPI, helping you create flawless prints every time.

What are pixels?

Pixels are the building blocks of digital images. Each pixel is a tiny square of color, and when combined, they form the complete image you see on a screen. The resolution of an image is determined by the number of pixels it contains, expressed in dimensions like 1920x1080 (width x height).

The larger the pixel count, the higher the resolution of your image. This translates to more detail and clarity, making your artwork stand out. Here’s a basic example:

Low-resolution image (800x600 pixels): Fine for small web graphics but won’t hold up for larger prints.
High-resolution image (3000x2000 pixels): Ideal for creating crisp, detailed posters or canvases.

When preparing your artwork for print, always consider the pixel dimensions. A low-resolution image may look fine on a screen but can appear blurry or pixelated when printed.

Understanding DPI (dots per inch)

If pixels are the building blocks of your image, DPI (dots per inch) is how those blocks are used in printing. DPI measures the density of printed dots within an inch to create a visual image. Put simply, a higher DPI means more detail in your print.

DPI vs. PPI

It’s important to differentiate between DPI and PPI (pixels per inch). PPI refers to the resolution of an image on a screen, whereas DPI is specific to printing. While both are related, they serve different purposes in the creative process.

Common DPI Standards:

72 DPI: Suitable for web images but not for printing.
150 DPI: Perfect for canvas prints.
300 DPI: The gold standard for highly detailed poster prints.

Many people mistakenly believe that canvas prints require 300 DPI for optimal quality. In reality, 150 DPI is more than sufficient. The texture of the canvas naturally minimises any visible differences between 150 and 300 DPI.

How Pixels, DPI, and file size work together

The interaction between pixels, DPI, and file size determines the quality and size of your printed image. Here’s how they fit together:

Resolution vs. print size

The resolution (pixel dimensions) of your image directly affects its print size at a given DPI. For example:

A 3000x2000 pixel image printed at 150 DPI will result in a sharp 50x35 cm print.
The same image printed at 72 DPI will stretch to a 105x70 cm print—but with a noticeable loss in quality.

While higher DPI generally provides better detail, simply increasing DPI without adjusting pixel dimensions won’t improve image quality. Achieving the best results requires a balance between resolution and DPI.

File size

Higher-resolution images with a high DPI will naturally have larger file sizes. While this ensures quality, file sizes that are too large can slow down uploads and strain storage capacity. Tools like Photoshop or online compressors help reduce file size while maintaining quality.

Common mistakes to avoid

Even experienced creators can stumble when prepping files for print. Here are a few pitfalls to watch out for:

Low-resolution images for large prints: Never upsize a small image to meet print requirements; it will only result in blurry prints. Start with a high-resolution file.
Misinterpreting DPI's role in digital files: DPI doesn’t affect how an image looks on a screen; it only matters for printing.
Overcompressing files: While smaller files are easier to upload, excessive compression can strip away crucial details.

When you upload your file on Printumo, the platform automatically checks the resolution and ensures it meets the minimum requirements for your selected print size. If your file’s resolution is too low, we’ll notify you so you can make adjustments before moving forward.

Achieve Flawless Prints Every Time

Mastering file size, pixels, and DPI is an essential skill for every artist, dropshipper, or print-on-demand creator. When these elements work in harmony, your designs will translate beautifully onto prints.

Want more tips and tools to simplify your creative process? Explore our additional resources or connect with Printumo’s experts for personalised advice.