Engineering Tools & Calculators

Free engineering unit converter for HVAC: pressure, temperature, airflow, BTU/h, kW, tons, energy, torque, R-value, microns and more — metric and imperial.

Convert BTU/h to kW, tons of refrigeration, watts and horsepower instantly. Free HVAC capacity converter with formulas and examples.

Convert CFM to litres per second and cubic metres per hour. Free airflow unit converter for HVAC ventilation and duct design.

Convert imperial R-value to metric RSI and U-factor. Free insulation converter used for Canadian and US building codes.

Calculate sensible heat in BTU/h and kW from airflow and temperature difference using Q = 1.08 × CFM × ΔT, with metric inputs.

Calculate latent (moisture) heat load from airflow and humidity ratio difference in grains per pound: Q = 0.68 × CFM × Δgr.

Calculate total (sensible + latent) heat from airflow and enthalpy difference: Q = 4.5 × CFM × Δh. Includes tons and kW.

Calculate heat energy from mass, specific heat and temperature change. Results in kJ, BTU and kWh.

Estimate kWh and electricity cost for HVAC equipment from power draw, run hours and your utility rate.

Convert between COP, EER and kW per ton for air conditioners, heat pumps and chillers, with notes on SEER/SEER2.

Calculate refrigerant superheat from suction line temperature and saturated suction temperature, in °F and K.

Calculate liquid-line subcooling from saturated condensing temperature and liquid line temperature.

Calculate compressor compression ratio from suction and discharge gauge pressures converted to absolute pressure.

Calculate refrigeration capacity from refrigerant mass flow and evaporator enthalpy change, in kW, BTU/h and tons.

Calculate evaporator TD — the difference between entering air temperature and saturated evaporator temperature.

Calculate condenser split: saturated condensing temperature minus outdoor ambient temperature.

Free Ohm's law calculator: enter any two of voltage, current, resistance and power to solve the other two.

Calculate single-phase real power (W) and apparent power (VA) from voltage, current and power factor.

Calculate three-phase kW and kVA from line-to-line voltage, line current and power factor using √3.

Calculate three-phase line current from kW, voltage and power factor.

Calculate voltage drop for single or three-phase circuits by conductor size, material, current and length.

Calculate conductor resistance for copper or aluminum wire by AWG size and length.

Calculate air velocity in FPM and m/s in round or rectangular ducts from airflow and duct size.

Size a round duct for a target velocity from airflow, with metric output and nearest standard size.

Convert rectangular duct dimensions to equivalent round diameter for equal friction (Huebscher equation).

Estimate friction loss per 100 ft and for a duct run from airflow and round duct diameter.

Calculate air changes per hour from airflow and room volume.

Calculate required ventilation airflow in CFM and L/s from a target ACH and room volume.

Calculate conductive heat loss through a wall, ceiling, attic or floor from area, R-value and temperature difference.

Calculate heat loss through windows or doors from U-factor, area and temperature difference.

Estimate whole-building heat loss from walls, ceiling, floor, windows and air leakage. A quick estimate, not a full load calculation.

Calculate insulation thickness needed to reach a target R-value from the product's R per inch.

Calculate how many bags or bundles of batt insulation you need from area, coverage and waste.

Calculate blown-in insulation volume and bag count from attic area, depth and label coverage.

Calculate furnace heat output in BTU/h and kW from input rating and efficiency.

Calculate heating appliance efficiency from output and input.

Calculate electric furnace current and BTU/h output from kW and voltage, single or three-phase.

Calculate furnace temperature rise from supply and return temperatures and estimate airflow from output.

Estimate natural gas use in ft³, m³ and therms plus cost from appliance input, run hours and heating value.

Calculate appliance firing rate by timing the gas meter test dial.

Calculate fluid volume in a pipe in US gallons and litres from inside diameter and length.

Calculate linear thermal expansion of copper, steel, stainless, PVC, CPVC and PEX pipe.

Calculate hydronic water flow in GPM and L/s from heat load and temperature drop (BTU/h = 500 × GPM × ΔT).

Convert pump differential pressure to feet and metres of head, with specific gravity correction.

Calculate pump brake horsepower from flow, head, specific gravity and efficiency.

Calculate heat exchanger effectiveness from inlet and outlet temperatures (cold side as minimum capacity).

Personal protective equipment checklist for HVAC technicians. Printable and free.

Step-by-step energy isolation checklist for HVAC equipment. Printable and free.

Electrical safety checks before, during and after HVAC electrical work. Printable and free.

Fall protection and ladder checks for rooftop and attic HVAC work. Printable and free.

Seasonal HVAC preventive maintenance checklist. Printable and free.

Start-up and commissioning checklist for new HVAC systems. Printable and free.