Walk down the power tool aisle of any hardware store, and you'll encounter a barrage of numbers: 750W, 18V, 5.0Ah, 80Nm, 2500RPM. For newcomers, these specifications can be overwhelming and seemingly meaningless. Yet understanding these numbers is crucial for choosing the right tool for your needs and getting the best performance from your equipment.
This guide demystifies power tool specifications, explaining what each measurement means, how they relate to real-world performance, and how to compare tools effectively. Whether you're a first-time buyer or an experienced user looking to deepen your understanding, you'll find practical insights to inform your purchasing decisions.
Power: Watts and What They Mean
Wattage is the most common specification for corded power tools. Watts (W) measure the rate of energy consumption—essentially, how much electricity the motor draws from the power point. Higher wattage generally indicates a more powerful motor, but the relationship isn't perfectly linear with performance.
Input vs Output Power
Here's an important distinction that catches many buyers: most power tool specifications show input watts (power drawn from the outlet), not output watts (power delivered to the task). Due to motor inefficiency, friction, and heat loss, output power is always lower than input power.
A tool rated at 750W input might deliver 500W or less as actual cutting or drilling power. This is why two tools with identical wattage ratings can perform quite differently—motor efficiency and design quality matter significantly.
📊 Typical Wattage Ranges
Common power tool wattage ratings:
- Light-duty drills: 350-500W
- Standard drills: 600-800W
- Hammer drills: 800-1200W
- Angle grinders (115mm): 700-900W
- Angle grinders (125mm): 850-1200W
- Circular saws: 1200-1800W
- Mitre saws: 1400-2000W
- Routers: 900-2400W
Voltage: The Cordless Power Indicator
For cordless tools, voltage (V) is the primary power specification. Voltage indicates the electrical potential difference that drives current through the motor. Higher voltage generally means more potential power, assuming other factors are equal.
Common Voltage Platforms
- 12V: Compact, lightweight tools for light-duty work. Excellent for tight spaces and occasional use.
- 18V: The most popular platform, offering good balance of power and weight for most tasks. Suitable for most DIY and many professional applications.
- 20V Max: Marketing terminology used by some brands (DeWalt, others). Actually equivalent to 18V nominal—the "20V max" is peak voltage when fully charged.
- 36V / 40V: High-power platforms for demanding applications, approaching corded tool performance.
- 54V / 60V: Professional-grade platforms for the most demanding applications, often using electronic switching to optimise power delivery.
When comparing across brands, be aware that nominal voltage ratings can differ slightly. A Makita 18V tool operates on the same principle as a DeWalt 20V Max tool—the numbers reflect different measurement conventions.
💡 Understanding FlexVolt and BiTurbo
Some brands offer dual-voltage batteries (like DeWalt FlexVolt 54V or Bosch BiTurbo 36V) that can operate in both high-voltage and standard 18V modes. These provide extra power for demanding tools while maintaining compatibility with the 18V tool ecosystem.
Ampere-Hours: Battery Capacity
For cordless tools, ampere-hours (Ah) measure battery capacity—essentially, how long the battery can deliver power before needing recharge. Think of voltage as pressure and ampere-hours as the size of the tank.
Capacity and Runtime
A 2.0Ah battery can theoretically deliver 2 amps for one hour, or 4 amps for 30 minutes, or 1 amp for 2 hours. In practice, power tool motors draw varying amounts depending on load, so runtime depends heavily on what you're doing. Drilling pilot holes uses less power than driving long screws into hardwood.
Common battery capacities range from 1.5Ah (compact, lightweight) to 5.0Ah or higher (maximum runtime). Higher capacity batteries are heavier, so there's a trade-off between runtime and tool weight/balance.
Power Considerations
Higher capacity batteries not only run longer but can also deliver more current, which can improve performance in high-draw situations. A 5.0Ah battery might outperform a 2.0Ah battery even in short bursts, as it can supply higher current without voltage drop.
Torque: Rotational Force
Torque measures rotational force—how much twisting power the tool can apply. It's measured in Newton-metres (Nm) and is particularly relevant for drills, impact drivers, and similar tools.
Understanding Torque Ratings
Impact drivers often boast impressive torque figures—200Nm, 300Nm, or more. However, these are typically peak torque values during impacts, not sustained torque. The pulsing action of impact drivers delivers torque in repeated bursts, which is why they can achieve high values without transferring equivalent reaction force to your wrist.
For drills, torque ratings are more directly comparable to actual performance. A drill with 60Nm torque can drive larger fasteners into harder materials than one rated at 30Nm.
Adjustable Torque (Clutch Settings)
Most quality drills feature adjustable torque settings (the numbered ring near the chuck). Lower settings limit torque to prevent overdriving screws or stripping heads. Higher settings allow maximum torque for demanding tasks. Learning to use the clutch effectively prevents damage and improves results.
Speed: RPM and Impact Rates
Rotational speed is measured in revolutions per minute (RPM). Higher RPM means faster drilling or driving, but isn't always better—some materials and fasteners require slower speeds for optimal results.
Variable Speed
Most quality power tools offer variable speed control through trigger sensitivity. Starting slowly helps prevent bit wander and material damage, while full speed increases efficiency once the cut or hole is established.
Impact Rates (IPM)
Impact drivers and some hammer drills list impacts per minute (IPM) alongside RPM. This indicates how frequently the impact mechanism strikes. Higher IPM can improve performance but generates more noise and vibration.
✅ Brushless vs Brushed Motors
Brushless motors are increasingly standard on quality cordless tools. They offer 25-50% more runtime per charge, longer motor life, and better power-to-weight ratio compared to brushed motors. While brushless tools cost more initially, the efficiency gains often justify the premium for regular users.
Practical Comparison Tips
When comparing tools, consider these practical approaches:
Match Specs to Application
A high-powered tool isn't always the best choice. For delicate work or tight spaces, a lighter, more manoeuvrable tool may be preferable. Consider what you'll actually be doing most often.
Look Beyond Peak Specs
Manufacturers often highlight maximum or peak specifications. Look for sustained or nominal ratings when available. Consider motor efficiency, build quality, and brand reputation alongside raw numbers.
Consider the System
For cordless tools, you're buying into a battery platform. Consider the full range of tools available on that platform, battery options, charger quality, and long-term availability. A slightly less powerful tool on a better-supported platform may be the wiser choice.
Real-World Reviews
Specifications tell only part of the story. User reviews and professional tests reveal how tools perform in actual use. Look for feedback from users with similar applications to your own.
Summary: Specifications in Context
Power tool specifications provide useful comparison points, but they're not the whole picture. Understanding what each number means helps you make informed decisions, but remember that build quality, ergonomics, reliability, and service support matter just as much as raw power figures.
Focus on your actual needs: the materials you work with, the tasks you perform most often, and how the tool feels in your hand. The best tool is one that helps you work safely and efficiently—and that's not always the one with the biggest numbers on the box.