Every project starts with the right number.
Pick a tool off the wall, give it your measurements, and walk out with a buy list in gallons, boxes, cubic yards or wire gauge, with waste margin and code tables already figured in.
Wire Size
AWG for the load and the run
Answer in AWGVoltage Drop
What a long run costs you
Answer in % dropConduit Fill
Trade size for the wires you pull
Answer in trade sizeService Load
100, 150 or 200 amp service
Answer in ampsGenerator
Running watts plus the surge
Answer in wattsRecessed Lighting
How many cans, and how far apart
Answer in fixturesWatts & Amps
The power triangle, solved
Answer in wattsMeasure. Hang. Buy.
Most calculators stop at an area ("you need 180 square feet"), which isn't what the shelf sells. Every PlankMath tool converts your room into purchase units: coats and coverage into gallons, square footage plus waste into sealed boxes, depth into cubic yards and bag counts, amps and distance into a wire gauge. The assumptions are printed on the tag, where you can change them.
- Output comes in the units stores actually sell.
- Coats, waste %, coverage rates and code tables are yours to adjust.
- The number lands as you type, and the how-it-works text sits below it.
- Copy the buy list, or copy a link that holds your numbers.
From the guides
A calculator hands you a quantity. It can't tell you whether you measured the right surface, or whether the coverage rate it assumed matches the label on your can. These guides cover that part. They were written while building the formulas, and you can check them against your own project.
- How much paint do you actually need
Why 350 square feet per gallon is only a starting point.
- How to measure a room properly
The step before every calculator, and the one that costs the most when it goes wrong.
- Why you buy 10% more flooring than your room
Waste allowance is material the installation really uses. What sets the number.
- Sizing an air conditioner: what BTU actually means
Bigger is worse. Why oversizing an air conditioner makes a room clammy instead of cool.
One project, several tools
A bathroom is drywall, then paint, then flooring, then a circuit for the fan: four numbers over three weekends, and by the time the third matters nobody remembers the second. A free account keeps them together in a named project, so the buy list you worked out in March is still there in May.