Free calculators for electrical, HVAC, plumbing, and structural work, in imperial units and to the codes you actually cite. No account, no paywall.
Wire and conduit, voltage drop, load and breaker sizing.
Heat loss, duct and refrigerant sizing, airflow.
Pipe sizing, drainage, fixture units, water heaters.
Beams, columns, footings and spans in wood, steel, concrete.
Insulation, R and U-values, moisture, acoustics, materials.
Unit converters and reference data for the field.
No sign-up, no paywall, no gated numbers. Ads keep every calculator free to use, whether you are at a desk pricing a job or on-site with gloves on. Every result shows its units and the code behind it, so you can defend the number on a bid or a plan.