HVAC & Energy calculators
Choose a task below. Check each calculator’s assumptions and units before using its result.
AC Tonnage Calculator - Home Cooling BTUs & Square Feet
Calculate air conditioner cooling tonnage and required BTU/hr capacity based on square footage, climate zone, and home insulation.
Air Changes Per Hour Calculator - Room CFM & Ventilation
Determine room air turnover rates, required exhaust fan CFM, and compliance with ASHRAE standards.
Air Handler Cooling Coil Condensate Drain Sizing Calculator
Calculate moisture removal rates (GPH), minimum P-trap water seal depth for draw-through air handlers, and IPC code drain pipe sizing.
Air-Side Economizer Dry-Bulb & Enthalpy (Free Cooling) Calculator | AnythingOnline
Free air-side economizer calculator. Determine dry-bulb and differential enthalpy changeover thresholds, free cooling capacity (BTU/hr & Tons), and avoided chiller kW.
ASHRAE 62.2 & IRC Whole-House Mechanical Ventilation Calculator | AnythingOnline
Free ASHRAE 62.2 residential ventilation calculator. Calculate continuous mechanical fresh air CFM, air changes per hour (ACH), and code compliance per IRC M1505.
Backflow Preventer Sizing & Pressure Drop Calculator
Calculate hydraulic head loss (PSI), minimum required city main pressure, and assembly pipe size for ASSE 1013 RPZ and ASSE 1015 Double Check backflow valves.
Blower Door Test ACH50 & CFM50 to Natural Infiltration Calculator | AnythingOnline
Free blower door calculator. Convert CFM50 to ACH50 and natural infiltration (ACHnat), calculate Effective Leakage Area (ELA), and check 2021/2024 IECC code compliance.
Boiler Blowdown Calculator - Cycles of Concentration
Optimize surface continuous blowdown rates, maintain target boiler water TDS levels, prevent mineral scale carryover, and quantify unrecovered thermal energy losses.
Boiler Horsepower Calculator - Steam Output & BTU
Convert boiler horsepower (BHP) into actual steam generation (lbs/hr), thermal output in BTU and kW, factor of evaporation, and fuel firing input requirements.
Chilled Water Thermal Storage (TES) Tank Calculator
Size naturally stratified chilled water storage tanks, verify inlet diffuser Froude numbers to preserve thermoclines, and quantify peak electrical demand reduction.
Cold-Climate Heat Pump Heating Capacity & COP Derating Calculator | AnythingOnline
Free cold-climate heat pump derating calculator. Calculate heating capacity (BTU/hr) and COP drops at 17°F, 5°F, and -15°F, auxiliary heat strip kW, and hourly operating costs.
Commercial BESS Peak Shaving & Utility Demand Charge Savings Calculator | AnythingOnline
Free commercial BESS peak shaving calculator. Size battery storage (kW/kWh), calculate monthly and annual electric demand charge savings ($/kW), round-trip efficiency losses, and ROI payback.
Compressed Air Receiver Tank Storage Volume & Cycle Time
Size air receiver tanks (Gallons & Liters) to absorb peak pneumatic demand, eliminate motor short-cycling, and calculate compressor pump-up recharge duration.
Condensate Pipe Sizing Calculator - Flash Steam & Flow
Calculate flash steam generation percentage when hot condensate drops in pressure across steam traps and size two-phase condensate return lines.
Cooling Tower Cycles of Concentration & Blowdown Calculator
Balance cooling tower water chemistry, calculate evaporation, blowdown, and makeup GPM flow rates, and quantify water and sewage utility savings from increasing COC.
Data Center CRAC/CRAH Airflow & Aisle Containment Calculator
Calculate total cooling CFM requirements, evaluate rack Delta-T heat extraction, compare aisle containment architectures, and eliminate costly recirculation hot spots.
Dehumidifier Sizing (Pints per Day & Moisture Load) Calculator | AnythingOnline
Free dehumidifier sizing calculator. Determine pints per day (PPD) capacity for basements and homes based on square footage and moisture conditions.
Dew Point & Enthalpy Calculator - Psychrometric Chart
Calculate psychrometric air properties including dew point, wet bulb, specific humidity, and total heat enthalpy.
Direct-Fired Makeup Air Calculator - CFM & MBH Sizing
Size dedicated outdoor makeup air units to balance kitchen and factory exhaust hoods, calculate sensible heating MBH, and verify ANSI Z83.4 combustion air purity standards.
Duct Air Velocity (FPM) & Noise Criteria (NC) Grille Calculator | AnythingOnline
Free duct air velocity and noise criteria calculator. Calculate face velocity (FPM), velocity pressure, and NC sound ratings for HVAC grilles and diffusers.
Ductwork External Static Pressure (ESP) & Blower Sizing
Calculate total HVAC system External Static Pressure (in w.g.), supply/return friction, MERV filter drops, wet coil resistance, and blower fan CFM curves.
ERV Latent & Sensible Energy Recovery Ventilation Calculator | AnythingOnline
Free ERV energy recovery ventilator calculator. Compute sensible (SRE) and latent recovery (LRR), delivered fresh air temperature, moisture transfer (pints/day), and heating/cooling BTU savings.
Firewood BTU & Wood Stove Heating Cord Consumption Calculator | AnythingOnline
Free firewood BTU calculator. Calculate heat output per cord across wood species (oak, maple, ash, pine), moisture content penalty, and winter heating cords needed.
Free API Oil-Water Separator Sizing Calculator
Size industrial oil-water interceptor basins using Stokes' Law (API 421). Calculate free oil droplet rise velocity, required basin surface area, and chamber dimensions.
Free Battery C-Rate & Peukert Runtime Calculator
Calculate real-world battery discharge runtime and effective capacity under heavy C-rates using Peukert’s equation for LiFePO4 and Lead-Acid.
Free Chilled Water Loop Sizing & Flow Rate Calculator
Size central chilled water loops. Calculate cooling flow rate (GPM) from chiller tonnage, temperature differential (ΔT), pipe diameter, and friction loss.
Free Chimney Draft & Flue Sizing Calculator
Determine chimney stack effect draft pressure (Pascals / "WC), required flue diameter, and exhaust CFM flow for wood stoves and fireplaces.
Free Commercial Grease Interceptor Sizing Calculator
Calculate total kitchen fixture drainage flow (GPM), recommended PDI certified trap size, and minimum required grease retention capacity in pounds.
Free Cooling Tower Approach & Range Calculator
Calculate cooling range, approach to ambient wet-bulb, heat rejection tons, thermal effectiveness, evaporation loss, and blowdown makeup water rates.
Free Direct Evaporative Cooler Sizing Calculator
Calculate leaving supply air temperature from ambient wet-bulb depression, required airflow CFM for room volume, sensible cooling BTU/hr, and water evaporation rate.
Free Drainage Fixture Unit (DFU) Calculator
Calculate total drainage fixture units (DFUs), size horizontal drain branches, building sewer pipes, and vertical stacks per IPC and UPC codes.
Free EV Charging Time & Cost Calculator
Calculate hours to charge, total electricity cost per session, grid kilowatt-hours consumed, and cost per 100 miles for electric vehicles.
Free Furnace Size & Heating BTU Calculator
Determine heating BTU capacity, climate zone load factors, AFUE efficiency ratings, and furnace sizing based on home square footage.
Free Gas Pipe Sizing Calculator
Determine the correct pipe diameter, maximum BTU capacity, gas flow rate (CFH), and pressure drop for natural gas and propane lines using NFPA 54 / IFGC tables.
Free Heat Pump COP vs Gas Furnace Savings Calculator
Compare heat pump COP operating costs against gas and propane heating systems.
Free Hot Water Recirculation Pump Sizing Calculator
Size domestic hot water recirculation pumps, calculate piping heat loss (BTU/hr), determine GPM return flow, and calculate total dynamic head loss.
Free HRV Sensible Heat Recovery Efficiency Calculator
Calculate CSA C439 Sensible Recovery Efficiency (SRE), delivered supply air temperature, thermal power recovered (BTU/hr & kW), and electric defrost pre-heater requirements.
Free HVAC AHU Condensate P-Trap Sizing Calculator
Calculate minimum P-trap vertical drop ($A$), trap outlet rise ($B$), and total water seal depth to prevent drain pan backup in negative-pressure draw-through AHUs.
Free Hydronic Expansion Tank Sizing Calculator
Calculate thermal expansion volume, diaphragm tank sizing, acceptance factor, and pre-charge pressure for closed-loop hydronic heating boilers.
Free Hydronic Expansion Tank Sizing Calculator
Size diaphragm and bladder expansion tanks for closed hydronic boilers and glycol loops using ASME Section VIII standards to absorb thermal water expansion.
Free Hydronic Heating Expansion Tank Sizing Calculator
Size diaphragm and bladder expansion tanks for closed-loop hydronic heating systems per ASME Section VIII. Calculate water volume expansion and tank acceptance factor.
Free Hydronic Snow Melt Sizing Calculator
Calculate ASHRAE Chapter 51 radiant snow melting heat flux (BTU/hr/ft²), back losses, glycol circulation GPM, and boiler gross kW capacity.
Free MPPT Solar Charge Controller Sizing Calculator
Calculate cold-weather maximum open-circuit voltage ($V_{oc,max}$), array charging amperage, and required MPPT controller specs to prevent controller blowouts.
Free Pipe Thermal Expansion Loop Calculator
Calculate axial thermal expansion growth, required U-bend expansion loop dimensions, guide spacing, and anchor forces for steam and hydronic piping.
Free Pool Sand Filter Sizing Calculator
Determine filter surface area, pump flow rate (GPM), turnover cycles, minimum backwash fluidization rates, and sand media replacement weight for swimming pools.
Free Room Lux & Lumens Lighting Calculator
Calculate target illumination lux, total lumens, and LED fixture counts for rooms.
Free Solar Battery Fuse & Wire Ampacity Calculator
Calculate inverter DC current, continuous fuse rating per NEC 125% rule, copper cable gauge (AWG), and round-trip voltage drop for 12V, 24V, and 48V battery banks.
Free Solar Panel Payback Period Calculator
Calculate solar installation break-even timeline, tax credit savings, and 25-yr ROI.