When you want to mount something heavy on the wall, just putting in the right screw won’t work for long. If the thing is too heavy, it will eventually pull the screw out from the wall
That’s why while mounting anything on drywall the most practical thing to do is using a wall anchor plug. And you need to make a pilot hole first to insert it on the wall.
Knowing how to determine drill bit size for a wall anchor plug will help you create the right-sized hole for the wall plug. The hole, the plug, and the screw, all have to be of similar and corresponding sizes to work properly.
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Deciding on The Screw and Wall Anchor/Plug
When you’re a hammer, everything in the world looks like a nail. And when you’ve got a drill in hand, making holes on anything seems just right. But don’t just start poking with any drill bit yet and ruin the wall.
The drill bit needs to correspond with the size of the screw and wall anchor as well. You don’t want a useless hole to ruin the perfect wall, do you?
The first order of business is to select the right screw. This is fairly easy since you just need to pick the one that will be able to withstand the weight of the furniture, painting, or anything else that you want to mount.
Then you’ll have to pick the correct wall plug which is determined by the screw that you’ve just selected. Both need to be compatible in size, otherwise, the plug won’t support the screw.
If the anchor plug is too big the screw will loosen and come off easily. And if it is too small it won’t fit the screw at all. It has to be just long enough for the screw to fit in. The length of the wall plug will also have to be the same or a little bit longer than the screw.
But if you’re still confused as to which plug to choose for the screw some numbers might help. In general case scenarios, yellow plugs are used for 4-8 gauge screws, the red plug goes well with 6-10 gauge screws, 10-14 gauge screws are perfect for brown plugs, and finally blue plug for 14-18 gauge screws.
Don’t worry if you find it hard to memorize. We’ll provide a table showing these numbers in an easy-to-follow format later.
Related Article: Tap Drill Bit Size Chart
Types of wall anchors
You must be wondering, why do I need to know about wall anchor types when I need to know the size of drill bits? Well, actually the drilling will depend on the size of the wall anchor. So without knowing its types and sizes, you’ll likely make mistakes with drill bit sizes.
Although you’ll find some other types apart from these, there are mainly four types of wall anchors.
1. Plastic expansion anchors
This is the most commonly used anchor and also tends to be the weakest of them all. Made of plastic, it expands when you drive the screw inside. They almost look like a jacket with ribs. Plastic expansion anchors have a good gripping ability of both the screw and the wall.
2. Self-drilling drywall anchors
Self-drilling anchors look like screws themselves. You can screw them without any predrilled hole on the wall. These anchors can handle very heavy objects. When you drill it, the sharp threaded drilling end flips to press up against the back of the drywall.
3. Molly bolts
Although these bolts might look similar to the small plastic anchors they can hold many heavy-duty objects. Mostly used by professional builders, molly bolts are easy to install and secure.
The unique thing about molly bolts is that you can remove and reinstall the screw from it without compromising the anchor. Molly bolts are usually made of plastic or zinc-plated steel. When you drive these bolts into the wall, its metal sleeve expands creating an anchor inside the wall.
4. Toggle bolt
These bolts use the traditional anchor method with two parts: the toggle and the machine bolt. Toggle bolts are the preferred solution for heavy items since they possess strong holding power.
You’ll need to make a pilot hole first to install these bolts into the wall. However, metal toggle bolts are sometimes difficult to keep level in the wall while installation.
Determining the drill bit size
This is the part where the size of the drill bit has to be considered. The previously mentioned different colored anchors clearly show that not all of them are of the same size or style. This means there is no standard drill bit that you can install on the wall.
When you want to drill the concrete wall for the wall anchor plug, choose a drill bit that is slightly smaller than the plug itself since you want the anchor to stick inside the drilled hole as tightly as possible. Here you find the best drill bits for the concrete walls.
When your drill bit is slightly smaller than the plug, some light tap with a hammer helps it stick inside with an interference fit. If you can’t choose which drill bit to use, start with a smaller one first to make a pilot hole and work your way up.
Remember we told you we’d share an easy chart matching the drill bit sizes to the wall plugs? Well, here it is. It shows you the corresponding size needed of wall plugs and drill bits for each screw size.
| Screw size | Wall plug color | Drill bit size |
| 4-8 | Yellow | 5 |
| 6-10 | Red | 6 |
| 10-14 | Brown | 7 |
| 14-18 | Blue | 10 |
What if the plug sizes are unknown?
Occasionally, it may happen that the plug isn’t one of the colors listed here. What do you do then? How do you determine which drill bit to use for the wall plug? A simple test could help you determine the drill bit size in such situations.
Take a piece of cardboard and drill it with a bit that you think is appropriate for the plug. Be careful while drilling so that the hole doesn’t get larger than the diameter of the drill bit. So, take measures not to move the drill sideways while you’re doing it.
Read More: What Are Spade Drill Bits Used For?
Now take the plug and see if it fits into the hole in the cardboard with its teeth catching the sides. If the hole seems too small use a larger drill bit. If you, however, find the hole too big for the plug and see not even its teeth getting stuck on the hole then select a smaller drill bit.
This process might take a bit longer but it is worth the trouble than having an extra dill on the wall.
Final words
Wall plugs are of great benefit when it comes to sticking a screw on the wall. It helps the screw to hold on tightly and not fall off. However, the right-sized drilling is a precondition for the plug to do its job. So you must know how to determine the drill bit size for the wall anchor and wall plug correctly.