Heating, Cooling & Insulation Calculators

Explore heating, cooling, ventilation and insulation estimates for a room or home. Start with the BTU, furnace or heat loss tools when planning heating capacity, and use airflow or fan calculators to estimate ventilation needs. Other tools cover insulation quantities, electricity costs, lighting, solar panels and water heating. Results depend on the dimensions and assumptions you enter; climate, air leakage and equipment efficiency can make a large difference. Compare the explanation on each page with your building and product specifications. Use these estimates for early planning and comparisons, then confirm equipment sizing and installation details with the appropriate project assessment.

Choose a calculator

• Attic Ventilation CalculatorNet free vent area for a loft or attic by the 1/150 or 1/300 rule, split between eaves and ridge.Open calculator →
• Bathroom Exhaust Fan CalculatorExtractor fan airflow in CFM or m³/h for a bathroom, by volume and by floor area.Open calculator →
• BTU CalculatorCooling or heating capacity for a room in BTU/h and kW, adjusted for insulation, sun and occupants.Open calculator →
• CFM Duct Airflow CalculatorEstimate volumetric airflow from the internal section of a duct and its measured average air speed.Open calculator →
• Dehumidifier Size CalculatorWhat capacity of dehumidifier, in litres or pints per day, a damp room or basement needs.Open calculator →
• Electricity Cost CalculatorRunning cost of any appliance from its wattage, hours of use and your price per kWh.Open calculator →
• Firewood CalculatorStères, cords and face cords in a woodpile, and how much firewood a heating season needs.Open calculator →
• Furnace Size CalculatorCompare a known design heating load with a furnace's rated output, and estimate required fuel input from rated efficiency.Open calculator →
• Room Heat Loss CalculatorHeat loss of a room through walls, windows, roof and air leakage, in watts and BTU/h.Open calculator →
• Insulation CalculatorInsulation thickness for a target R-value or U-value, plus layers and rolls or boards to buy.Open calculator →
• Room Lighting CalculatorLumens a room needs for its use, and how many LED bulbs or downlights deliver them.Open calculator →
• Solar Panel CalculatorHow many solar panels and what system size cover your yearly electricity use, and whether they fit the roof.Open calculator →
• Water Heater Size CalculatorTank size in litres or gallons from household size and your busiest hour of hot water use.Open calculator →
• Watts to Amps CalculatorConvert real input power into current for DC, single-phase AC or balanced three-phase AC.Open calculator →