If you don't know your specs, you can't start your project. PicMonkey's here to help. Read this guide for all things sizing, dimensions, and conversions!
Optimal File Resolution How Many Pixels in 8.5x11, px to in
How Can I Convert from Pixels to Inches for Printing?
Inches to Pixels, Convert Inches to Pixels Online
Changing default Pixel to Inches - Pre-V2 Archive of Affinity on
Pixels, images, and files
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The 72 PPI Web And Screen Resolution Myth
Pixel Chart : r/coolguides