Free tools

Furnace calculators

Size your furnace, estimate operating costs, compare models and project your savings — all free, no signup.

Furnace Size Calculator

Find the right furnace size for your home in square feet.

Calculate the heating BTUs your home needs by climate zone.

Estimate your monthly operating cost based on efficiency.

Estimate the installed cost to replace your furnace.

Compare any furnaces side-by-side on specs and price.

See your annual savings from upgrading to high efficiency.