Terms of use

Last updated October 14, 2026

By using sizesums.com you agree to these terms. They're short; please read them.

SizeSums is run by Data Dingo (NIP 8942982912).

Estimates only

Our calculators give estimates for planning. The right size for your home depends on details we can't see: its construction, air leaks, ducts, windows and how you use it. For central air conditioning, furnaces and heat pumps, a qualified contractor's Manual J load calculation is the final word.

Electrical and gas work

Wire, breaker and circuit results follow commonly published National Electrical Code values, but your local code, the equipment's installation instructions and your inspector decide what is allowed. Electrical, gas and generator connections must be done by a qualified person and permitted where required. Never connect a generator to house wiring without a transfer switch.

Climate data

Climate zones and design temperatures are county-level values from public government data and our own calculations from it, shown under every result. Your site can differ, especially in hills, valleys and near the coast.

No warranty

The site is provided "as is", without warranties of any kind. We work to keep the math right and explain every formula, but we don't guarantee that results are complete, accurate or suitable for your project.

Limitation of liability

To the extent the law allows, SizeSums is not liable for any loss or damage arising from your use of the site or reliance on its results, including equipment purchases or installation decisions made using its results. Nothing in these terms limits liability that cannot be limited by law.

Ads and links

The site shows ads and may link to other websites. We don't control and aren't responsible for their content, products or practices.

Using our content

You're welcome to use the calculators and share links to them. Please don't copy the site's pages, text, data tables or code wholesale, or use automated tools to scrape it.

Changes

We may update these terms; the date at the top shows the latest version. Questions? Email hello@sizesums.com.