Everyday calculators, worked out at the kitchen table

Quick, honest answers to the small math questions of running a home. Each tool shows its formula and assumptions. Free, no sign-up, nothing you type leaves your browser.

• What size generator do I need for my house?
• How long will my propane tank last?
• How do we split a utility bill between roommates fairly?
• How much does it cost to run a space heater?
• What size window air conditioner do I need?
• How many gallons of paint do I need for a room?
• How many cubic yards of mulch or gravel do I need?
• How much will gas cost for my trip, and what is each person's share?
• How much does my refrigerator or freezer cost to run?
• What gauge extension cord do I need for my amps and length?