What paper size should I use to print coloring pages?

Letter (8.5×11") for North America and A4 (210×297mm) elsewhere — the coloring pages on Coloring-Pages.com are sized to print cleanly on either with no scaling adjustment needed. For larger format, scale to 150% in your printer dialog (loses some sharpness) or use the PDF download which preserves quality at any size up to 11×11 inches.