Somewhere in your house is an appliance you have never actually calculated the running cost of, a water heater sized by whatever the previous owner happened to install, and an internet plan you picked based on a sales pitch instead of your actual usage. Most home decisions get made on gut feeling because doing the real math is annoying. We built six free calculators specifically so you do not have to.
Air Conditioner BTU Calculator
Buying an AC unit that is too small means it runs constantly and never actually cools the room. Too large, and it short-cycles, leaving the air cold but damp while wearing out the compressor early. This one factors in square footage, ceiling height, sun exposure, and occupancy, based on ENERGY STAR and DOE guidance, to get you a real BTU target before you shop.
Home Internet Speed Calculator
Add up your actual household, simultaneous 4K streams, work calls, gamers, smart devices, and get a real minimum Mbps instead of whatever number an ISP rep threw out. Also useful for the opposite problem: figuring out if your slow internet is actually a speed issue or just weak Wi-Fi coverage.
Appliance Running Cost Calculator
Plug in any appliance’s wattage and how long you run it, and see exactly what it costs per day, month, and year using your real electricity rate. Comes with a reference table of common appliance wattages if you do not know your specific numbers offhand.
Thermostat Savings Calculator
ENERGY STAR reports an average 8% savings on heating and cooling from certified smart thermostats. Enter your monthly bill and see what that percentage actually translates to in real dollars for your household.
LED Bulb Savings Calculator
LED bulbs cost more upfront and that is usually where people stop doing the math. This one shows the real annual cost comparison against incandescent, plus what the roughly 25x longer lifespan actually saves you in replacement bulbs over time.
Water Heater Size Calculator
Undersizing a water heater means running out of hot water mid-shower, regularly. This one uses DOE peak-hour demand guidance based on household size and bathroom count to recommend an actual tank size, not a guess.
All six are free, live-update as you type, and explain exactly how the math works instead of just spitting out a mystery number. Find all of them anytime on our Tools page.
Last Updated: August 2026.
