HVAC and Plumbing Calculators

Working with hvac & plumbing quantities

Sizing heating and cooling by square footage alone is the reason so many systems are oversized. An oversized unit short-cycles, never runs long enough to dehumidify, and wears out faster than a correctly sized one. Treat a rule-of-thumb BTU figure as a sanity check on a proper load calculation, not a substitute for one.

Worth knowing: A full Manual J load calculation accounts for insulation, window area, orientation and air sealing. On any system you are paying to install, it is worth the extra step.

These 9 calculators cover about 24,320 searches a month between them. Every one prints the formula it uses and a worked example, so you can check the result by hand before you order.