Power tool wattage chart: running and starting watts
Running, extra starting and total starting watts for circular saws, miter saws, table saws, drills, grinders and compressors, with a source for every row.
Hub
Electrical & power for tools
Browse guides by topic and find the next step for your project.
This hub covers the power side of your tools: batteries and chargers, watts and inverters, extension cords, and the multimeter you use to check them. It does not cover house wiring. For outlets, panels or new circuits, call a licensed electrician.
Most problems here come down to three numbers: volts, amps and watts. A pack that won't charge, an inverter that trips, or a cord that gets warm often means one of them doesn't match. The guides show you which one, and where to find it on the label.
How to pick a guide:
- Battery won't charge? Ryobi battery won't charge starts with what the charger lights mean.
- Running tools off an inverter or generator? Start with the power tool wattage chart, then see what size inverter runs a circular saw.
- Buying or using a meter? Read the Klein MM700 spec guide, then the multimeter guides.
- Car or lead-acid battery? How many cells are in a 12-volt battery explains the basics.
Each cluster below starts with one main guide, then the smaller fixes. The calculators do the watt and amp math for you.
Safety basics for this job
- Test your meter, then the circuit, then the meter again. This is the live-dead-live check. NFPA 70E and OSHA both call for proving a circuit is dead with a working tester.
- Use a meter rated for the job. The CAT rating tells you where a meter is safe to use. Check it before you test anything bigger than a battery.
- Retire a damaged battery. A swollen, leaking, hot or smelly pack is done. Use the charger made for it, and the CPSC warns never to use reworked packs.
- Never feed house wiring from a tool outlet. Plugging a generator into a wall outlet is backfeeding. The CPSC warns it can kill utility workers.
Start here
What size inverter do you need to run a circular saw?
A 7-1/4-inch corded circular saw needs about 1,800 to 2,200 W continuous and 4,000 W surge. See the chart, the math and the 12 V battery draw.
Ryobi battery won't charge? Read the charger lights first
A Ryobi 18V battery that won't charge is usually too hot, too cold, drained or worn out. Read the charger lights, try the safe fixes, skip the myths.
Klein MM700 multimeter: specs, CAT ratings and who it suits
Klein MM700 specs from the manual: CAT IV 600V, True RMS, LoZ, 1000V, 10A. How it compares with the MM400, MM600 and Fluke 115/117, and safe use.
How many cells are in a 12-volt battery?
A 12-volt car or mower battery has 6 cells of about 2.1 volts each. Lithium 12V batteries use 4 or 3 cells. How to tell, and how to spot a dead cell.
Topics in this hub
Multimeters
The settings you'll actually use, symbols, continuity tests, CAT ratings and how to check a tool battery.
Batteries & chargers
18V, 20V MAX, 40V and more, amp-hours, charger light codes, and what to do with a pack that won't charge.
Watts, inverters & cords
Running and starting watts, inverter and generator sizing, sine wave types and the cord gauge for each tool.
Tools for this hub
- Inverter size calculator for power tools
- Generator wattage calculator
- Cordless battery runtime calculator
- Extension cord gauge calculator for tools
All electrical & power for tools guides
Klein MM700 multimeter: specs, CAT ratings and who it suits
Klein MM700 specs from the manual: CAT IV 600V, True RMS, LoZ, 1000V, 10A. How it compares with the MM400, MM600 and Fluke 115/117, and safe use.
What size inverter do you need to run a circular saw?
A 7-1/4-inch corded circular saw needs about 1,800 to 2,200 W continuous and 4,000 W surge. See the chart, the math and the 12 V battery draw.
Ryobi battery won't charge? Read the charger lights first
A Ryobi 18V battery that won't charge is usually too hot, too cold, drained or worn out. Read the charger lights, try the safe fixes, skip the myths.
Power tool wattage chart: running and starting watts
Running, extra starting and total starting watts for circular saws, miter saws, table saws, drills, grinders and compressors, with a source for every row.
How to use an analog multimeter (and read the needle right)
Zero the needle, pick the range, read the right scale and multiply. How to use an analog multimeter for volts, ohms and amps, and when not to.
How to test for voltage with a multimeter, safely
Check for voltage the safe way: a CAT-rated meter, a non-contact tester first and the NFPA 70E live-dead-live check. Outlets, cords and dead circuits.
How to read AC gauges (and the EPA rule you need to know)
Blue reads the low side, red the high side, and the colored rings convert pressure to refrigerant temperature. How to read them, and the EPA 608/609 rules.
How many cells are in a 12-volt battery?
A 12-volt car or mower battery has 6 cells of about 2.1 volts each. Lithium 12V batteries use 4 or 3 cells. How to tell, and how to spot a dead cell.
Cen-Tech digital multimeter guide: settings, specs and safe limits
How to use Harbor Freight's Cen-Tech multimeters, from its own manuals: dial settings, fuses, CAT ratings and when a budget meter stays off mains power.