HVAC Calculators
Air Changes Per Hour Calculator
Calculate air changes per hour from airflow and room dimensions, and compare the result against typical ACH targets by space type.
Air Horsepower Calculator
Calculate the theoretical air horsepower required to move a given airflow against a static pressure, before accounting for fan efficiency losses.
Airflow CFM Calculator
Calculate the airflow in CFM required to deliver a given heat load at a chosen supply-to-room temperature difference using the sensible heat formula.
BTU Calculator
Estimate the BTU output a single room needs for a window unit or mini-split, based on area, sun exposure, occupancy, and kitchen use.
COP Calculator
Calculate the Coefficient of Performance (COP) of a heat pump from useful heat output and electrical energy input.
Delta T Calculator
Calculate the temperature split (delta T) between supply and return air for cooling or heating mode and check it against normal diagnostic ranges.
Duct Static Pressure Calculator
Estimate total external static pressure from duct length, fittings, friction rate, and component losses to check against blower capacity.
Duct Velocity Calculator
Calculate air velocity inside a duct in feet per minute (FPM) from airflow (CFM) and duct cross-sectional area.
EER Calculator
Calculate the Energy Efficiency Ratio (EER) of a cooling system from cooling output in BTU/hr and power input in watts.
Friction Rate Calculator
Calculate duct friction rate in inches of water gauge per 100 feet from total pressure drop and duct length.
Furnace Size Calculator
Estimate the required furnace input BTU rating from heat loss and AFUE efficiency, accounting for combustion losses at a given efficiency tier.
Heat Pump Sizing Calculator
Calculate both cooling and heating load for a heat pump and size equipment to whichever load governs, with the design driver identified.
HVAC Duct Sizer Calculator
Calculate the required round duct size from airflow and design velocity using the velocity method, rounded to standard duct sizes.
HVAC Load Calculator
Estimate total cooling and heating load in BTU/hr and tonnage from area, climate zone, insulation, occupants, and windows using a Manual-J-style method.
Latent Heat Load Calculator
Calculate latent heat load in BTU/hr from airflow and moisture grains difference using the standard 0.68 HVAC formula.
R-Value to U-Value Calculator
Convert an insulation or building assembly R-value into its corresponding U-value for use in heat load calculations.
Refrigerant Charge Calculator
Calculate total refrigerant charge for a split system using the manufacturer factory-charge method, adjusted for actual line set length.
SEER Rating Savings Calculator
Compare annual energy cost between an old and new SEER-rated cooling system based on cooling load, run hours, and electricity rate.
Sensible Heat Load Calculator
Calculate sensible heat load in BTU/hr from airflow and temperature difference using the standard 1.08 HVAC formula.
Ton to BTU Calculator
Convert HVAC cooling or heating capacity from tons to BTU per hour using the standard 12,000 BTU per ton conversion.
Sizing Comfort Correctly
An oversized or undersized HVAC system both waste money — one from excess capacity never used efficiently, the other from constantly struggling to keep up. These ten calculators cover load calculation, ductwork, and equipment sizing math.
What a Higher SEER Rating Is Actually Worth
SEER ratings scale roughly proportionally, so the jump from SEER 10 to SEER 16 can cut cooling energy cost by more than a third over the system's life — a meaningful gap once spread across a typical 10-15 year equipment lifespan. Run your own numbers with the SEER Rating Savings Calculator.
Popular HVAC Calculators
- HVAC Load Calculator — estimates a building's heating and cooling load from size, insulation, and climate.
- Duct Static Pressure Calculator — checks whether ductwork resistance falls within the system's designed operating range.
- Heat Pump Sizing Calculator — matches heat pump capacity to a building's heating and cooling demand.
Related: Heat & Energy Calculators for the underlying thermal math, Home Improvement Calculators.