Calculators
Each calculator shows its formula and assumptions under the result, so you can check the math yourself.
- 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.