A drill and an impact driver are both rotary driving tools that are helpful to have around the home, shop, or garage. Because they share some similarities, they are often confused with each other, but a drill and an impact driver are different enough that it's worth having each tool on hand to cover a wide spectrum of building and repair needs.
What a Drill Is
Available in corded or cordless options, a drill rotates a drill bit clockwise to bore holes in materials by cutting and removing waste materials. A drill applies constant torque. Equipped with a driver bit, a drill can turn screws, bolts, and other fasteners into materials. The drill can reverse to remove the fasteners.
Users supplement the rotary power by pushing onto the drill from the back. Also, when drills bog down, one common trick to coax them along is to deliver short bursts by quickly pressing the trigger several times. It's these supplementary actions that relate the drill to the impact driver and that sometimes lead owners of drills to explore purchasing an impact driver.
Greater utility than impact driver
Can both drill and drive
Low-cost bits and drivers
Poor at driving long fasteners
Difficult fasteners require pre-drilling
Hard on the hand, wrist, and arm
What an Impact Driver Is
An impact driver is shaped like a drill but usually it is shorter and smaller. It has many of the same features as a drill, such as a handle, trigger, and a type of chuck called a hex collet.
The difference between an impact driver and a drill is that an impact driver delivers the sequential bursts of power users often try to get with drills more effectively. It delivers those bursts automatically, without the user having to do anything.
An impact driver also drills at a constant speed as needed and draws upon the bursting action when the driver senses resistance in the work material.
Impact drivers powered by air compressors have long been used in the garage for vehicles. Small, cordless, lightweight impact drivers are a newer tool for home improvement.
Driving fasteners with great torque is the forte of impact drivers, not drilling holes. While you can use an impact driver in a pinch to drill a hole, that's not what it's best used for.
Easy on wrist and arm because torque is applied by the tool
Reduces chance of stripped screws
Smaller than most drills
High power ratio when compared to its size
No variable speeds
Poor for drilling
Not for hard, brittle materials like masonry
Requires special, expensive bits
More expensive than a drill
When to Use a Drill
Use a drill for boring holes with drill bits, for driving small fasteners into soft wood, and for drilling into masonry.
Owning an impact drill means that you can switch to using that for all fasteners except for the smaller ones. Because an impact drill is so powerful, it tends to draw in short screws faster than you might expect. This can result in pulling in the screw deeper than you want.
One application where this is particularly important is when driving drywall screws into drywall. You need to have precise control to prevent the screw head from drawing below the paper level and into the gypsum core. A drill will give you that level of control; an impact driver will not.
When to Use an Impact Driver
Use the impact driver when you want to drive most fasteners, except for very short ones.
An impact driver is especially good for uses like driving 3-inch screws into wood, a task that is difficult for a drill even with pre-drilling the hole. Impact drivers excel at driving fasteners into dense or knotty wood.
You'll also want to use an impact driver for machine bolts or lag bolts.
Should You Buy a Hammer Drill?
A hammer drill combines rotational bursts with front-to-back movement (the hammering action) to bore into difficult masonry that presents an obstacle for ordinary drills.
If an impact driver has less utility than a drill, then a hammer drill has less utility than either of those two tools—at least for most homeowners. Purchase a hammer drill only if you anticipate doing a lot of drilling into masonry. Otherwise, consider renting or buying one.