BTU Calculator
Sizing & LoadRoom-by-room heating and cooling load in BTU/h from area, climate zone and envelope.
BTU/h · Manual J
HVAC calculators and tools
Every calculator runs in your browser, prints cleanly and asks for nothing. Grouped by the part of the system they measure.
Sizing & Load
5 tools · 4 guides
Manual J load, BTU/h, tonnage, duct sizing and static pressure — the numbers that decide what equipment goes in.
AC Unit Size Calculator
Sizing & LoadTonnage for a whole house, with the oversizing check most rules of thumb skip.
tons · sq ft
Duct Size Calculator
Sizing & LoadRound and rectangular duct sizes from CFM and friction rate, with equivalent diameter.
CFM · in. w.c./100 ft
Manual J Load Calculator
Sizing & LoadA room-by-room worksheet that follows the ACCA Manual J method, printable.
BTU/h · room by room
Static Pressure Calculator
Sizing & LoadTotal external static pressure from supply and return readings, against the rated maximum.
in. w.c. · TESP
Heating
3 tools · 5 guides
Furnaces, heat pumps and the efficiency ratings that price them — AFUE, HSPF2 and the cold-climate question.
Furnace Size Calculator
HeatingInput BTU/h and output capacity from load, climate zone and AFUE.
BTU/h · AFUE
Heat Pump Sizing Calculator
HeatingCapacity at design temperature, balance point and the supplemental-heat gap.
BTU/h · balance point
AFUE Fuel Cost Calculator
HeatingAnnual heating cost from AFUE, fuel price and load — gas against electric.
$/yr · AFUE
Cooling
3 tools · 5 guides
Air conditioners, mini splits, refrigerant and SEER2 — the cool side of the manifold.
SEER2 Savings Calculator
CoolingAnnual cooling cost and payback when you move from one SEER2 rating to another.
SEER2 · $/yr
Mini Split Sizing Calculator
CoolingBTU/h per zone and how many heads a house actually needs.
BTU/h · zones
Superheat & Subcooling Calculator
CoolingTarget superheat and subcooling from pressures and temperatures, with the charge verdict.
°F · psig
Service & Costs
4 tools · 5 guides
Replacement cost, maintenance, filters and the credits that move the price — what the job costs and what keeps it running.
HVAC Replacement Cost Calculator
Service & CostsInstalled cost band by system type, tonnage and region, with the line items.
$ · installed
Air Filter Size Chart
Service & CostsNominal against actual filter dimensions, searchable, with the common sizes.
in. nominal
HVAC Maintenance Checklist
Service & CostsA printable spring and fall checklist with the readings a tech should record.
spring · fall
MERV Rating Chart
Service & CostsMERV 1–16 against particle size, pressure drop and what each rating catches.
MERV 1–16