HVAC Calculators — Duct Sizing, Load, CFM, BTU & SEER
Six calculators covering the residential HVAC workflow: size the load, split the airflow, size the ducts, pick the unit, and quantify the efficiency upgrade. Built on the same methods the metal ductulator and Manual J use — equal-friction sizing, area-share airflow, 400 CFM per ton — with every rule of thumb stated where you can check it. Estimates are honest about being estimates; formal designs belong to ACCA Manual J/D.
More HVAC Calculators
Duct Size Calculator
Enter CFM and friction rate — get the round duct diameter, the standard size to order, velocity, and the full size chart.
HVAC Load Calculator
Square footage, climate zone and house details in — get the estimated BTU, tonnage and a size breakdown you can defend.
CFM Calculator
Room airflow three ways: share of the whole-home CFM by area, air changes per hour, or tonnage × 400 — all in one place.
Room BTU Calculator
Room size, sun, occupants and kitchen use in — get the BTU and the mini-split or window unit size to buy.
Ton to BTU Converter
Convert either direction between tons, BTU/h and kW — with the common system sizes pre-mapped in a table.
SEER Savings Calculator
Old SEER, new SEER, annual kWh and your rate in — get the new consumption, kWh saved and dollars per year.