Job Site & Tools generator calculators
Tool motors are brutal on generators: a circular saw that cuts at 1,400W can spike well past 2,000W at trigger pull, and an air compressor starting against pressure is one of the hardest loads a portable generator ever sees. These calculators size for the tool with the largest surge — the same staggered-start math used everywhere on this site, but with loads that start and stop dozens of times an hour — and flag the 240V equipment, like larger welders, that needs a 240V-capable unit outright.
Pick your calculator
Power Tool Generator Size Calculator
Generator sizing for job-site tools: sourced running and trigger-pull surge watts for drills, circular saws, miter and table saws — size for the biggest motor.
Open calculator →Air Compressor Generator Size Calculator
Air compressor generator sizing by HP: sourced running and starting watts — including why starting against tank pressure makes this the hardest common jobsite load.
Open calculator →Welder Generator Size Calculator (120V & 240V)
Running a welder on a generator: input watts vs output amps, sourced figures for 120V wire-feed (~2,400W) and 240V machines (~7,000W), plus the clean-power caveat.
Open calculator →Electric Pressure Washer Generator Calculator
Electric pressure washer on a generator: sourced watts (~1,500W running, ~3,100W starting), the GFCI nuisance-trip fix, and when gas washers make more sense.
Open calculator →
Which calculator should I use?
Size for the biggest single motor you will run, then add whatever runs alongside it — a compressor cycling in the background changes the math for every other tool. The power tools calculator lets you pick the dominant tool by type; the air compressor page handles the cycling-load case; the welder page is mostly about the 120V-vs-240V decision, because welder input power is what the generator must supply, not the welding output. The electric pressure washer rounds out the set for cleanup work.
Running several of these at once? Themulti-appliance builder adds them up with the staggered-start surge math, and the outage scenarios cover the common combinations pre-built.