HomeSizerSizing worksheets for US homes

Home equipment sizing calculators

Six worksheets for sizing equipment in a US house. Each one shows the formula, a worked example and the code section or manual it comes from. Nothing you enter leaves your browser.

Last updated 6 sheets · 4 systems

1. Water & Septic2 sheets

2. Electrical1 sheet

3. Heating & Cooling2 sheets

4. Power1 sheet

How to read a sheet

  1. Numbers and rules come from published sources: state regulations, the NEC, U.S. DOE, ENERGY STAR, university extension services and manufacturer sizing guides. Each one is checked against a second source.
  2. Code results (septic tank, wire size) are minimums under the rule cited. Your local code can be stricter. Confirm with your local authority or a licensed pro.
  3. Rule-of-thumb results (AC, generator, water heater) are a starting point for the talk with your contractor. They do not replace a design for your site.