How big, how much, how long: home questions worked out with real numbers.
Calculators and plain guides for your house, yard and home tech. Every number comes from published specs or public data, and every page shows how we got there.
Calculators
- Power station size calculator
List what you want to keep running in an outage and get the battery size, inverter rating and runtime you need.
- Appliance electricity cost calculator
Add your devices and your electricity rate to see what each one costs per hour, month and year.
- Paint calculator
Enter room size, doors, windows and coats to see how many gallons of paint to buy, with a gallons-plus-quarts option.
- Mulch, soil and gravel calculator
Work out cubic feet, cubic yards and bags of mulch, topsoil or gravel for a bed or path from its size and depth.
- Dehumidifier size calculator
Get the ENERGY STAR pint size for your square footage and dampness level, plus the monthly cost to run the dehumidifier.
- Lawn fertilizer calculator
Enter lawn size and the bag's N-P-K numbers to get pounds of fertilizer per 1,000 sq ft, total pounds and how many bags to buy.
- AC BTU calculator
Find the BTU/h a room air conditioner needs from the ENERGY STAR chart, adjusted for sun, people and kitchen use.
- Grass seed calculator
Pounds and bags of grass seed for a new lawn or overseeding, using university extension seeding rates for 9 grasses.
- Christmas lights cost calculator
Add light strands, inflatables and projectors to see watts, cost per night and per season, and whether one 15-amp circuit can carry it.
- Concrete bag calculator
Cubic feet, cubic yards and the number of 40/50/60/80 lb concrete bags for a slab, post holes or round tube forms.
- Shower cost calculator
What one shower costs in water plus water heating, electric or gas, per shower and per year, with 2.5 vs 2.0 gpm savings.
- Generator size calculator
List what you'll run in an outage to get running watts, peak starting watts and a recommended generator size with a 90% margin.
- Roofing calculator
Turn house footprint and roof pitch into roof area, squares and shingle bundles to buy, with editable waste and bundles per square.
- Water leak cost calculator
See how many gallons a dripping faucet or running toilet wastes and what it costs per month and year at your water rate.
- Attic insulation calculator
Enter your climate zone and current attic insulation to see your R-value, the ENERGY STAR target and inches to add.
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