Find Your Flue Size with Our Fireplace Calculator

Need to determine the right flue liner size for your fireplace? Our free Flue Size Calculator makes it easy! Simply input your fireplace opening dimensions (width and height in millimeters), and we’ll recommend the appropriate Isokern Pumice Flue Liner diameter based on the industry-standard 15% free area rule. Whether you’re upgrading your chimney or installing a new fireplace, this tool provides a quick starting point for your project.
Disclaimer: This calculator is intended as a general guide only. Flue sizing can vary based on specific installation requirements, local building codes, and fireplace design. For accurate and safe results, always consult a professional installer or chimney specialist before making any decisions or purchases.