Terms of Use
Last updated: September 2, 2026
Estimates, not engineering
Free BTU Calculator provides sizing estimates based on widely used rule-of-thumb methods. They are intended for general guidance when shopping for room air conditioners, space heaters and similar equipment. They are not a substitute for a load calculation (such as ACCA Manual J) performed by a licensed HVAC professional, and they do not account for every factor that affects a real room. Manufacturer ratings, local building and electrical codes, and professional advice take precedence over anything on this site.
No warranty
The site and its content are provided “as is” without warranties of any kind, express or implied, including accuracy, fitness for a particular purpose, or non-infringement. We work to keep the formulas correct and clearly documented, but we cannot guarantee that any result is suitable for your situation.
Limitation of liability
To the fullest extent permitted by law, Free BTU Calculator and its operator are not liable for any loss or damage arising from use of this site, including equipment purchases, installation decisions, energy costs, or property damage. Your use of the site is at your own risk.
Acceptable use
You may use the calculators and read the content freely for personal or commercial purposes. You may not scrape the site at a rate that degrades it for others, republish substantial portions of the content without attribution and a link, or present the results as a professional engineering assessment.
Advertising and third parties
The site may display advertising and link to third-party websites. We do not control and are not responsible for third-party content or products. See our privacy policy for how advertising and analytics partners handle data.
Changes
We may update these terms from time to time; the date above reflects the current version. Continued use of the site after changes constitutes acceptance. Questions: contact us.