A door peephole lets you see who is outside without opening the door, and it is one of the simplest security upgrades you can make. Learning how to install a peephole takes about 15 minutes, requires only a drill and one bit, and costs under $15 in materials. Whether you are adding a viewer to a new door or replacing an old scratched lens, the process is straightforward on wood, fiberglass, and steel doors alike.
Choosing the Right Peephole
Standard peepholes use a wide-angle lens rated at 160 to 200 degrees of viewing angle. A 200-degree viewer lets you see visitors standing off to the side, not just directly in front of the door. Most peepholes fit doors between 1-3/8 and 2-1/4 inches thick, which covers virtually every residential entry door in the US.
Basic brass or chrome peepholes cost $5 to $10 at any hardware store. Upgraded options include UL-listed fire-rated viewers ($12 to $20) required on apartment doors in some jurisdictions, and digital peephole cameras ($30 to $80) that display the view on a small LCD screen on the inside, eliminating the need to press your eye against the lens. For a standard installation, a mechanical wide-angle viewer from brands like Prime-Line or Defender Security works perfectly.
Tools and Materials
You need very little for this project. Gather the following before you start:
- Peephole viewer kit (includes the lens barrel and interior eyepiece)
- Power drill (corded or cordless)
- Hole saw or spade bit in the diameter specified by the peephole kit (typically 1/2 inch for standard viewers)
- Painter’s tape
- Tape measure and pencil
- Small flathead screwdriver or coin (for tightening the two halves together)
Marking the Correct Height
The standard peephole height is 58 to 60 inches from the finished floor, which accommodates adults of average height. If the primary user of the peephole is significantly shorter or taller, adjust accordingly. Some homeowners install a second peephole at 42 to 48 inches for children or wheelchair users.
Measure from the floor up and mark the height on the interior side of the door with a pencil. Center the mark left to right on the door stile. On a 6-panel door, position the peephole in the solid wood area between the top two panels. On a flush door, center it on the width of the door. Use a level or a square to confirm your mark is not drifting left or right.
Drilling the Hole
Place a strip of painter’s tape over both sides of the door at the drilling location. The tape prevents splintering on wood doors and reduces chipping on fiberglass or steel surfaces. Mark your drill point on the tape on the interior side.
For wood and fiberglass doors, use a standard spade bit or hole saw at the diameter specified by your peephole kit. Most require a 1/2-inch hole. Drill from the interior side of the door to prevent blowout on the finished exterior face. Apply steady, moderate pressure and let the bit do the work. When the pilot tip of the spade bit pokes through the exterior side, stop drilling. Walk to the exterior side and complete the hole by drilling back through from that side. This two-direction technique gives you clean edges on both faces.
For steel doors, switch to a bimetal hole saw or a step drill bit designed for metal. Run the drill at a lower speed to avoid overheating, and apply a drop of cutting oil to the bit. Deburr the hole edges with a metal file or sandpaper after drilling.
Installing the Peephole Viewer
A peephole consists of two threaded halves: the lens barrel that inserts from the exterior side and the eyepiece that screws in from the interior side. Remove the tape from both sides of the door and clear any debris from the hole.
Insert the lens barrel through the hole from the outside of the door. The lens flange should sit flush against the exterior door surface. From the inside, thread the eyepiece into the barrel by hand. Tighten by gripping the exterior lens barrel with one hand (or have someone hold it) while turning the interior eyepiece clockwise with a coin or flathead screwdriver inserted into the tightening slot.
Tighten until both halves are snug against the door surfaces with no wobble. Do not overtighten, as excessive force can crack the lens housing on plastic models. The viewer should feel solid and not rotate when you press your eye against it.
Tips for Special Door Types
Steel Doors
Steel doors are hollow between the two metal skins, filled with foam insulation. The drilling process is the same, but use a metal-rated bit and expect the bit to punch through two thin layers of steel with insulation in between. Apply a small bead of clear silicone caulk around the exterior flange before tightening to seal against moisture infiltration.
Fiberglass Doors
Fiberglass doors cut cleanly with standard wood bits. The main risk is splintering the gel coat on the exterior face, so always tape both sides and drill from the inside first. A brad-point drill bit produces the cleanest hole in fiberglass.
Thick Doors
If your door is thicker than the peephole’s rated range, you need an extended-length viewer. These are available in lengths up to 3-1/2 inches for commercial doors and cost $12 to $18. Measure your door thickness before purchasing to ensure the viewer threads have enough engagement to pull both halves tight.
Maintenance and Upgrades
Clean the lens on both sides with a soft cloth and glass cleaner every few months. Dust and fingerprints degrade the view over time. If the lens fogs or develops internal condensation, the seal between the two halves has failed and the unit should be replaced.
For a significant security upgrade, consider swapping a mechanical peephole for a digital door viewer. Models like the Ring Door View Cam ($80 to $130) replace the peephole entirely and add motion-activated video recording, two-way audio, and smartphone notifications. They install in the same 1/2-inch hole and run on a rechargeable battery. Whatever option you choose, a peephole is one of the fastest and most affordable security improvements you can make to any entry door.
