Recognized standards.
All 46 Calculators
Heating Load Calculator
Estimate room heating load based on room size, orientation, insulation, and outdoor design temperature.
Boiler Size Calculator
Calculate required boiler capacity from heating load, DHW demand, efficiency, altitude, and safety margin.
Radiator Sizing Calculator
Calculate the number of radiator sections needed based on room heating load and water temperatures.
Pipe Flow Calculator
Calculate pipe diameter, flow rate, or velocity given any two parameters. Supports water and air.
Pipe Insulation Calculator
Determine the required insulation thickness for pipes based on allowable heat loss.
Pump Head Calculator
Calculate required pump head and estimated power based on flow rate, pipe size, and pipe length.
Cooling Load Calculator
Estimate cooling load using the unit index method with orientation, insulation, and window corrections.
Duct Sizing Calculator
Calculate duct dimensions, airflow, or velocity for rectangular and circular ducts.
Expansion Tank Size Calculator
Calculate required expansion tank volume based on system volume, temperature change, and pressure.
BTU Calculator
Estimate cooling and heating BTU/h for any room. Get instant BTU, tonnage, and kW results.
AC Size Calculator
Determine what size air conditioner you need in tons, BTU/h, and kW.
Furnace Size Calculator
Calculate required furnace BTU output based on heating load and AFUE efficiency.
Heat Pump Size Calculator
Calculate the right heat pump size for your home. Determines cooling and heating capacity, recommended tonnage.
Water Heater Expansion Tank Calculator
Calculate the required expansion tank size for your water heater system based on capacity, pressure, and temperature.
CFM Calculator
Calculate required airflow (CFM) for any room based on room size and air changes per hour (ACH).
HVAC Unit Converter
Convert between power, air flow, pressure, temperature, length, area, velocity, volume, energy, and efficiency units.
Ohm's Law Calculator
Calculate voltage, current, resistance, or power using Ohm's law. Enter any two values to find the rest.
Watts to Amps Converter
Convert watts to amps (or amps to watts) for DC, single-phase, and three-phase AC circuits.
Amps to Watts Converter
Convert amps to watts (or watts to amps) for DC, single-phase, and three-phase AC circuits.
AWG to mm² Converter
Convert American Wire Gauge (AWG) to cross-sectional area in mm² and diameter in mm.
Capacitor Code Decoder
Decode 3-digit ceramic capacitor codes to pF, nF, and μF values instantly.
Resistance Calculator
Calculate series and parallel resistance combinations for any number of resistors.
Energy Consumption Calculator
Estimate kWh energy usage and electricity cost for any appliance over hours, days, or months.
HP to kW Converter
Convert between horsepower (HP) and kilowatts (kW) with efficiency adjustment.
RC Time Constant Calculator
Calculate the time constant (τ = R × C) and charge/discharge timing for RC circuits.
Voltage Divider Calculator
Calculate output voltage for 2-resistor or 3-resistor voltage divider circuits.
Electricity Cost Calculator
Calculate the daily, monthly, and yearly electricity cost for any appliance based on wattage and usage.
Lumen Calculator
Calculate required lumens for any room based on area and recommended illuminance level.
Insulation Resistance Tester
Evaluate insulation resistance at reference temperature and determine pass/fail based on voltage rating.
Conduit Offset Bend Calculator
Calculate offset distance, shrink, and bend marks for electrical conduit offset bends.
Electrical Quote Estimator
Generate a professional electrical project quote with materials, labor, overhead, and profit margin.
Electrical Power Calculator
Calculate real, reactive, and apparent power for DC, single-phase, and three-phase systems.
Voltage Drop Calculator
Calculate voltage drop, percentage drop, and minimum wire size for any circuit.
Transformer Calculator
Calculate transformer voltage ratio, current, and kVA rating for single-phase and three-phase.
Power Factor Correction Calculator
Calculate required capacitor size (kVAR and μF) to improve power factor and reduce energy costs.
Motor Current Calculator
Calculate full-load current (FLA) and starting current for AC motors with various starting methods.
Circuit Breaker Sizing Calculator
Size circuit breakers per NEC standards for continuous loads, motor circuits, and general use.
Wire Ampacity Calculator
Calculate wire ampacity with temperature and bundle correction factors per NEC Table 310.16.
Wire Size Calculator
Determine minimum wire size based on both ampacity and voltage drop requirements.
Conduit Fill Calculator
Check conduit fill percentage per NEC Chapter 9 for EMT, PVC, and rigid metal conduit.
Electrical Box Fill Calculator
Calculate box fill volume per NEC 314.16 and verify against box capacity.
Electrical Load Calculator
Calculate service demand load per NEC Article 220 for residential and commercial buildings.
Solar Panel Calculator
Estimate solar panel system size, number of panels, and payback period based on energy usage.
Dehumidifier Size Calculator
Calculate required dehumidifier capacity (pints/day) from room area, current humidity, and target humidity.
SEER Savings Calculator
Calculate energy savings when upgrading from old SEER to new SEER. Annual savings, payback period, and 10-year net savings.
Ventilation CFM Calculator
Calculate required ventilation CFM per ASHRAE 62.2. Input floor area and bedrooms for minimum mechanical ventilation rate.
About This Site
These free HVAC and electrical calculators are built on publicly available engineering formulas and methodology references. They provide early-stage sizing estimates for heating, cooling, ductwork, hydronic piping, radiators, insulation, pump selection, electrical circuits, wiring, and more.
These calculators are intended for preliminary design estimates. Always verify final designs against local codes, project specifications, and professional engineering requirements.
HVAC Design Guides
Electrical Design Guides
Standards Comparison
Local HVAC Sizing Guides by Region
Climate-specific sizing rules and city-level HVAC design references across the United States.