We understand the importance of high quality paper in a planner! All of our planners are created using at least 100gsm (27lb.), bright white paper. All of our paper is thick enough that most pens (including our planner pens!) and markers will not bleed through the pages. Some items do have paper thicker than 100gsm (ex: Hanging Calendars: 165gsm, Monthly Planners: 180gsm paper) so be sure to check the item listings for exact details per product!