The connection between a tool’s unit watt output (UWO) and torque power rating has been widely discussed for many years. One of the most renowned brands, DeWalt, uses UWO calculations to showcase the overall functionality of their tools. However, there still seems to be some confusion regarding the true meaning of these terms and how they compare to traditional speed and torque measurements.

## Speed and Torque as Indicators of Power

Let’s start by understanding the roles of speed and torque in measuring power. Speed refers to how fast the chuck spins on the bit, while torque represents the force behind that speed. To put it in perspective, think of it in terms of a football game. A small wide receiver may be incredibly quick but lacks the strength to withstand tackles when caught—that’s speed without torque. On the other hand, a lineman has immense muscle power but lacks speed. The ideal combination lies in a tight end who possesses a balance of both speed and torque.

Yet, relying solely on speed and torque to determine tool power can be misleading if you don’t fully comprehend what you’re looking at. Achieving a balance between the two always involves trade-offs, which are more apparent in a three-speed rig.

## Translating the Speed and Torque Equation

Let’s dive deeper into how speed and torque translate in different modes. In Overdrive mode, you get maximum speed but considerably lower torque—similar to a wide receiver on the football field. Mode 2 strikes a well-balanced compromise between speed and torque. Low speed delivers the highest amount of torque but at a slower pace, akin to a lineman. It’s important to note that while all three modes offer the same power, the distribution varies.

It’s crucial to understand that when looking at maximum speed and torque, you’re not directly evaluating their combined power. The calculation is not as simple as multiplying the two values, as they cannot occur simultaneously. Instead, this requires an analysis of the relationship between speed and torque at a specific setting, which is more complex than a basic multiplication problem. To ensure accuracy, torque testing adheres to the Power Tools Institute’s (PTI) widely accepted standard.

## Evaluating Unit Watt Output (UWO) and Torque as Power Indicators

Unit Watt Output (UWO) is a calculation that involves multiplying speed and torque and dividing the result by a constant. This computation yields the power output in watts. Unfortunately, the specific constant value used in the calculation is not publicly disclosed, which can be frustrating for those seeking complete transparency.

Nevertheless, this calculation allows us to determine the maximum power output in watts at any given time. For example, suppose you have a drill that delivers 500 in-lbs of torque at 600 RPM. Using the maximum output power (MWO) calculation, you can compare its power to that of a drill providing 475 in-lbs of torque at 650 RPM.

## Comparing Speed, Torque, and Unit Watts Out

Comparing speed, torque, and unit watts out requires a bit of algebraic calculation, statistical analysis, and some number crunching. While it may not be rocket science, it can be quite daunting. However, with careful research, I managed to find some data that sheds light on the mysterious constant mentioned but never defined—around 560.

To simplify, we’re dealing with four figures: maximum speed, maximum torque, output in watts, and the constant 560 (represented as K). The equation, in its raw form without specific values, appears as follows: Speed (RPM) x Torque (in-lbs) / 560 = Maximum Power Output (estimated).

It’s important to remember that when using the peak torque value, you must also consider the maximum RPM at the same settings, particularly when dealing with multispeed rigs. This value will be the highest number within the lower range.

### Quick Case Study

Let’s take a closer look at one of DeWalt’s cordless drills—the DeWalt DCD790D2 Brushless Compact Drill. It has a rating of 360 per watt and a maximum speed of 600 RPM in high torque mode. By plugging this information into our power output vs. torque calculation, we find that the maximum torque for this 20V compact drill is approximately 336 in-lbs.

Suppose we have another DeWalt 20V Max XR drill spinning at 575 RPM in high-torque mode, offering 490 in-lbs of torque. Applying the same calculation, we determine that it has a unit watt rating of roughly 503 MWO.

## Limitations of the Unit Watt Output Equation

However, it’s important to acknowledge some inherent issues with the specific power output vs. torque equation. This equation often becomes a mere topic of conversation rather than a reliable tool. Firstly, maximum power delivery occurs before reaching top speed or applying maximum torque in any given mode—usually somewhere in between.

Another aspect to consider is the absence of a publicly available constant figure (K). I had to reverse engineer it by referencing a manual that provided gross watts, maximum torque output in Newton meters, and corresponding no-load maximum speed.

Furthermore, it’s worth noting that maximum torque does not necessarily coincide with maximum speed in this setup. Combining and utilizing these values as anything more than a rough estimate can be misleading.

In fact, the actual maximum torque for our DCD790 drill is 531 in-lbs, far deviating from the estimate provided by the equation.

### ToolGuyd Weighs In

Stuart, a ToolGuyd contributor with a Ph.D., delved into this subject matter and shared his insights. He made a compelling point:

“I know there’s no way to convert UWO to torque, and for a long time, I’ve been avoiding the math to prove it. Good news, I feel like I’ve maxed out UWO. Bad news, there’s no way to convert UWO to torque.”

He further elaborated that the problem lies in the unavailability of underload speed data, making it impossible to extract torque information from UWO. Additionally, there is no guarantee that UWO is measured at maximum torque and corresponding speed. Ultimately, UWO serves as a value without offering any useful cross-brand torque specifications.

As an SEO specialist and copywriter, I greatly respect Stuart’s expertise and findings, and I’m not offended by his discovery.

## Are Watts More Informative Than Speed and Torque?

The answer to this question is both yes and no. If your priority is to determine which drill possesses the highest overall power, considering specific power output is certainly a useful comparison tool. However, two drills may have the same wattage rating while one offers higher torque at low speed. In such cases, knowing the exact torque levels becomes essential. It’s crucial to acknowledge that DeWalt was correct in emphasizing that torque alone does not account for hole-drilling capacity—it’s the combination of speed and torque that produces results.

When calculating maximum torque, you connect the drill to a machine that measures the torque generated without turning the chuck. Conversely, calculating maximum speed involves determining the RPM when no friction acts upon the chuck. However, these calculations cannot perfectly replicate real-world situations encountered on the job. On the other hand, output per watt is measured by a machine that considers chuck speed and the amount of resistance (requiring torque) under various settings, providing engineers with the maximum output.

This comparison is most applicable to mode 2 on a three-speed rig. However, it’s essential to acknowledge that comparing the two approaches is like comparing two different languages while assuming they can be equally translated using a third language.

## The Final Verdict: Watt Output vs. Speed and Torque

So, what’s the bottom line? If you require the utmost torque for your specific application, knowing a drill’s maximum torque output becomes imperative. However, if your primary concern is overall wattage and achieving optimal results for most applications, unit watts out (UWO) is undoubtedly a valuable measure. Ideally, a comprehensive rating system combining both unit watts and maximum torque would provide users with truly informative data.

DeWalt’s decision to utilize Unit Watts Out (UWO) aligns with their understanding that consumers don’t solely base their purchasing decisions on maximum torque—a consideration I wholeheartedly agree with. Having an overview of the power ratings before commencing tests would be highly beneficial.

### Too Many Conversion Challenges

Unfortunately, one major obstacle is the lack of consensus among tool manufacturers regarding the preferred specification. It would be advantageous if manufacturers consistently included unit wattage in their spec sheets. For instance, DeWalt and Porter-Cable continue to publish torque ratings, allowing users to decide based on the power measurements that suit them best.

DeWalt was correct in asserting that torque cannot be accurately judged solely based on unit watt ratings. I understand the frustration associated with this issue—it frustrates me as well. The problem lies in the fact that maximum power delivery does not occur at peak torque or peak no-load speed. In reality, you may rarely—if ever—encounter the listed no-load speed or maximum torque values while using the tool.

Consequently, we are left with two imperfect rating systems that, nevertheless, serve their purpose if users understand the information each conveys. It’s important to keep these factors in mind when comparing the best impact driver with the best cordless drill.

Finally, an important note about the equation I provided: consider it irrelevant. Statistically, there are numerous variables to consider, and the resulting power and torque values in watts may deviate significantly from reality. Unfortunately, I cannot provide a specific percentage of inaccuracy—it will vary from tool to tool.