When you want to hang a heavy item on a wall, you need to attach it to a stud located behind the drywall. It's possible to hang lightweight items at any spot on the wall by using drywall anchors. But for shelves, cabinets, large mirrors, or anything heavy or fragile, it's safest to continue the fastener through the drywall and embed it in the underlying wood stud.
What Is a Stud and a Stud Finder?
A wall stud is a vertical two-by-four located behind interior drywall or plaster. A stud is positioned on edge so that its room-facing width is 1 1/2 inches. A stud finder is a device that locates the stud's position without penetrating the wall.
But first, you need to find the stud. Three categories of stud finders can help: electronic, magnetic, and phone-based.
Electronic Stud Finders
How They Work
Electronic stud finders are battery-powered devices that find studs by sensing changes in the density of the wall. Pressing a button on the device creates a magnetic field. This field sends feedback to the device when the density changes, like going from a hollow area to an area with a stud. The device displays a light or it beeps.
Edge stud finders signal when the device hits the left or right edge of a stud. Center or whole-stud finders cast multiple magnetic fields that capture the entire width of the stud and beyond.
The cost for edge finders is about $15 to $20, and the cost for whole-stud stud finders is $20 to $30.
Pros and Cons
Electronic stud finders offer one strong advantage over magnetic stud finders, and that's that they find the stud itself, not the metal fasteners. This is helpful for those long stretches between metal fasteners.
Also, magnetic stud finders require many broad sweeps, plus you must them move up and down. With electronic devices, you only need to sweep in a straight, horizontal line.
With edge stud finders, it can be tricky to move slow enough—and then instantly stop—the moment the device signals. And then you have to repeat the sweep from the opposite direction.
Electronic center stud finders help find the true width of the stud, but still only in increments. As you move the device, the magnetic field is passed from one sensor to an adjacent one. The set of signal lights will not refresh until the device has moved far enough.
Find stud, not fastener
Accurate up to 1 1/2 inches deep
Only need to sweep horizontally across wall
Can signal false positives
Must move device slowly
Require you to mark on the wall
Magnetic Stud Finders
How They Work
Magnetic stud finders rely on the presence of metal fasteners to find the stud behind the drywall. If drywall is attached to a stud, the reasoning is that there must be a screw or nail that holds the two together. Find the fastener and you've found the stud.
Rare earth, or neodymium, magnets are the key component to these stud finders. Before rare earth magnets were developed, weaker magnets that had to be directly on top of the fastener were used. Rare earth magnets can detect fasteners even as you approach the fastener.
The cost of magnetic stud finders is less than $10.
Pros and Cons
Magnetic stud finders are inexpensive, reliable, and battery-free. Magnetic stud finders deposit markers on the wall and remain on the wall until you remove them. Leaving several magnetic stud finder markers running vertically along a stud provides an accurate picture of the stud's location.
But it's easy to forget that magnetic stud finders aren't finding studs; they're finding metal. So, it's possible to hit false positives such as metal pipes or protective metal nail plates.
Drywall fasteners at the ends of drywall sheets are driven near the edge of the drywall, placing them slightly off-center to the stud, on both the left and right sides. So, with magnet stud finders, you need to average out several markers to find the centerline.
Batteries not required
Remain on wall as markers
Find fasteners, not studs
Do not locate center of studs
Require multiple, complex sweeps
Limited to surface fasteners
Stud Finders on Your Phone or Stud Finder Apps
How They Work
Stud finders for your phone consist of two main physical components: the scanning device plus cords and a smartphone. You provide the smartphone.
With the scanner attached to your phone, you run the scanner over the wall. When the scanner passes over a stud, a picture of a stud will appear on your screen.
Phone-based stud finders show a simplified representation of the stud, not the stud itself.
Pros and Cons
Stud finders for your phone make it easy to find a stud because you see what appears to be a stud. There is no need to translate flashing lights or beeps into physical objects. Many phone-based stud finders can also detect pipes, wires, and other foreign objects.
Stud finders for your phone can be an expensive investment for a tool that you may use infrequently. They typically cost between $75 and $125.
Visual representation of hidden studs
Find objects other than studs: pipes, wires
Require phone and app
Not compatible with all phones
How to Use a Stud Finder
Find the Stud's General Location First
With all stud finders, first locate the general area of the stud before finetuning the location with the device.
- Studs are always located at room corners and alongside windows and doors.
- The next nearest stud will be within 16 inches of a room corner.
- Adjacent studs will be located 16 inches apart from each other, measured from center to center.
- Some interior non-load-bearing walls (such as closet enclosures) may have studs placed at 24 inches.
How to Use an Electronic Stud Finder
Calibrate Stud Finder
Calibrate the stud finder by first placing it against the wall at any spot. Next, press the button until the device lights up.
Sweep Toward Stud
Slowly move the stud finder horizontally toward the stud.
- For edge stud finders, the device will light up and beep when it reaches the edge of the stud. Mark this location with a light pencil mark on the wall or on top of a strip of painter's tape.
- For center stud finders, continue moving the device over the stud area until the device registers the full width of a stud.
Sweep From Other Direction
For edge stud finders only, lift the device about six inches past the stud location. Press the device against the wall, then press the button. Slowly move back toward the stud again.
Mark Stud Again
When the device registers the edge of the stud, mark the location on the wall.
Troubleshooting Electronic Stud Finders
- Electronic stud finders operate quietly prior to finding the stud. Make sure that the device is turned on by sweeping over a known stud.
- Materials other than drywall (stone, concrete, tile, or plaster) can throw off stud finder readings. Unless the finder works with these other materials, confine your use to drywall.
- If the stud finder is not producing readings, it may not have been calibrated. Not all electronic stud finders need to be calibrated, but some do.
How to Use Magnetic Stud Finders
Sweep Near Stud
Press the magnetic stud finder against the wall near the suspected area of the stud. Sweep up upward in an S-shape.
Pull Away Magnet Holder
When you feel the holder lock onto the wall, stop moving. Release the holder, depositing the magnet marker on the wall.
Deposit Additional Magnets
Repeat the earlier steps with two or three more magnets on the same stud.
Find Centerline of Magnets
The vertical centerline between all of the magnets should be the center of the stud. Hold an aluminum or wood straightedge over the magnets and mark the centerline with your pencil.
Troubleshooting Magnetic Stud Finders
- If your fastener isn't hitting the stud, you may have incorrectly estimated the magnets' centerline. Run a laser level plumb line down the center of all of the magnets to get a perfect reading.
- Another way that magnets produce incorrect results is if they all happen to be on one side of the stud. Reposition the magnets so that some are on the left side of the stud and some on the right side.
How to Use Stud Finders for Your Phone
Plug Scanner to Phone
Use the provided cord to plug into your phone's audio or USB port, with the other end attached to the scanning device.
Download the app and synchronize your phone with the scanning device.
Lock the back of the phone onto the scanning device.
Choose Wall Type
Some phone-based stud finders ask you to select the type of wall being scanned, such as drywall, wood, or concrete.
Press the calibration button on the phone. Move the scanner in large circles on the wall.
Scan and Mark Wall
Press the scan button, then move the scanning device slowly across the wall. When you see an object, stop the scanner. Mark the wall with a pencil.
Troubleshooting Phone-Based Stud Finders
- If the scanning device is not operating properly with your phone, make sure that your phone is compatible. Some scanners work with Android phones but not iPhones.
- If the phone is compatible with the scanner and still is not working, make sure that your phone's software is up to date.
- If the wrong images appear, you may need to go back and re-select the category of materials.