Home & Utilities Calculators
Free home calculators for air conditioner sizing (AC tonnage and BTU) and the running cost of an appliance. Size cooling and control energy bills.
Home & Utilities Calculators - Cooling and Running Costs
Getting the size and cost of home equipment right saves money twice: once on the purchase and again on every energy bill. These calculators help you size an air conditioner to a room and see exactly what an appliance costs to run, using the same BTU and kilowatt-hour maths the pros rely on.
Four Home Calculators
AC Tonnage Calculator - Estimates the cooling capacity a room needs in BTUs per hour and tons, based on floor area, the number of occupants, sun exposure, and whether the room is a kitchen. Turns a room size into a recommended air conditioner size so you neither over nor undersize the unit.
Paint Calculator - Works out how many litres of paint a room needs from its dimensions or wall area, the number of coats, and the coverage per litre. Subtracts a typical allowance for doors and windows and rounds up to whole tins, so you buy enough to finish the job without waste.
Electricity Cost Calculator - Works out what a single appliance costs to run, per day, month, and year, from its wattage, hours of use, and your electricity rate. Ideal for comparing a heater, air conditioner, or old fridge against a more efficient alternative.
Fence Calculator - Finds the fencing material, number of posts, and total cost for a rectangular yard from its dimensions, post spacing, and prices.
Why Sizing and Running Costs Matter
An air conditioner that is too big cools the air fast but shuts off before it removes humidity, leaving the room clammy and cycling on and off in a way that wastes energy and wears out the compressor. One that is too small never catches up on a hot day. The AC Tonnage Calculator matches capacity to the room. On the cost side, a few high-wattage appliances dominate most bills, so knowing what each one costs with the Electricity Cost Calculator shows you where the savings are.
Frequently Asked Questions
What size air conditioner do I need for a room?
As a rough guide, a room needs about 20 BTU per hour per square foot, adjusted for occupants, sun, and kitchens. A 400 square foot room needs roughly 8,000 BTU, or about two-thirds of a ton. The AC Tonnage Calculator works out the exact figure.
How many BTU are in a ton of cooling?
One ton of air conditioning equals 12,000 BTU per hour. So a 24,000 BTU unit is a 2-ton system. The AC Tonnage Calculator reports both BTU and tons.
How do I calculate what an appliance costs to run?
Multiply the power in kilowatts by the hours of use to get kilowatt-hours, then multiply by your electricity rate. A 1,500 watt heater run 4 hours a day at 0.15 per kWh costs about 0.90 a day. The Electricity Cost Calculator shows the daily, monthly, and yearly totals.
Which appliances cost the most to run?
Anything that heats or cools: electric heaters, air conditioners, water heaters, tumble dryers, and old refrigerators. High wattage combined with long running hours drives the cost. Use the calculator to compare them and target the biggest savings first.