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How is MWO (Max Watts Out) measured?


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A Watt is a unit of measure for Power. 1 Watt = 1 joule per second. A joule is a unit of energy, heat, or ‘work’. Essentially it’s the rate of energy converted or transferred.


Think of it like this, if I pump in a bunch of electricity into a light bulb a few things happen. First light is produced. The amount of light that shins from the bulb is measured in Watts. It’s a ratio of energy from pumping electricity (volts) into the light bulb (resistance). The formula for power is (volts)^2/resistance, that =  total Watts.  The key concept is, it takes work to convert electrical energy into light and the amount of work is what we are interested in (Watts).


A byproduct from producing light is heat. The heat produced from the light can be calculated with a related power formula. In the example of the light bulb we would need to know the current the bulb requires to run. Knowing this we can calculate the dissipated power. Dissipated power is heat. As you can see the measurement Watt, can be used for more then just energy.


Substitute a motor for the light bulb in the above example. Electricity powers the motor and the motor creates mechanical movement. I think you can see how Watts can be derived from a simple equation. Things get complicated though, the motor uses gear reduction to change the torque and depending on what your drilling/impact, resistance/’current’ changes. What the tool guys do is account for best case ‘max’ values (MWO).


The RPM and Torque are dependent on the motor and voltage but more so on the gearing. RPM is speed and torque is force.


I don’t know if it’s a better way to measure the performance of a power tool but I suspect that because it’s a somewhat complicated theory, the OEM’s can throw meaningless numbers at people.. wow factor.


*Watt was discovered and named after James Watt, a Scottish engineer, thus because its a proper name we always capitalize Watt

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A good cost effective idea for dewalt would be to put a qr code on the package that will take you to info on the uwo unit watts out formula. Not everyone would want to or need to know so printing on a separate sheet of paper would be a waste but this way those that would like to know can, even while looking on the shelves at the store

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