⚡ Free home project calculators
Measure once. Calculate right. Buy the right amount.
Size wire, air conditioners, paint, tile and concrete in seconds — then learn what the numbers mean with plain-English guides for homeowners.
✓ Formulas shown on every page ✓ U.S. units and codes ✓ Safety notes included
Wire Size Calculator
Recommended copper wire
8 AWG
Load · voltage
20 A · 120 V
One-way run
75 ft
Voltage drop
2.0% ✓
12 AWG carries the load, but the long run needs 8 AWG to keep voltage drop under 3%.
Free calculators
Pick a project, get the numbers
Wire Size Calculator
Copper AWG gauge from amps, voltage and run length, with voltage drop checked.
Electricity Cost Calculator
What any appliance costs to run per day, month and year at your rate.
BTU Calculator
The right air conditioner size for a room, adjusted for sun, people and kitchens.
Paint Calculator
Gallons and quarts for walls and ceilings, minus doors and windows.
Tile Calculator
Tiles and boxes for a floor or wall, with waste for cuts and patterns.
Concrete Calculator
Cubic yards and 40, 60 or 80 lb bags for a slab, patio or pad.
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What Size Wire Do I Need? A Plain-English Guide to AWG
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Why HomeToolDesk
Shows the method
Every calculator explains its formula and assumptions, so you know where the number comes from.
Safety first
We flag when a job needs a permit or a licensed pro, especially for electrical and gas work.
Free and private
No sign-up. Calculators run in your browser and never store what you enter.