You know it’s important to have drainage holes in planters so excess water drains out. But no one mentions what size these drainage holes should be and how many you need.

You need 1/4th inch drainage holes when using a planter that is 12 inches or less in diameter. You need 1/2 inch drainage holes when using a planter that is larger than 12 inches in diameter. The number of drainage holes you need would be between 3-8 for a planter that is 4-12 inches in diameter.

I’ve created an easy-to-use chart below that will give you exactly what should be the size of the drainage holes and how many such holes you need in your planter.

How many drainage holes in a planter?

If you have a planter that is 4-6 inches in diameter, then you just need 3-6 drainage holes where each is 1/4th inch in size.

Planters that are larger than 6 inches would do well with 6-8 drainage holes and the size would be 1/4th or 1/2 inch depending on how big the planter is.

The idea of having these drainage holes should be how well they can drain the water from all parts of the planter but prevent soil from leaching out.

Diameter of pot (inches)No. of drainage holesSize of drainage holes (inch)Distance between drainage holes (inch)
431/41
661/42
881/42
1081/44
1281/44
1461/24
1661/26
1881/26
2081/26

How far should the drainage holes be spaced apart?

If you have a planter that is 4 inches or less in diameter, then it’s OK to space the drainage holes 1-inch apart.

If you have a 6-8 inches planter, then a space of at least 2 inches is to be kept between the drainage holes.

As the planter gets larger in size, you can increase the spacing to 4-6 inches, and that should work well for such planters.

Place one drainage hole at the center. And then you can place the remaining drainage holes closer to the edge.

It will also help if you are going to place rocks or broken pot pieces at the bottom of the planter. Since the drainage holes are spaced well apart, there are fewer chances of them getting blocked.

How do you cover the planter drainage holes?

The problem with drainage holes is that the potting soil can start falling out of them if they are large. This keeps happening when you water the potted plants.

So you need to add some material to the bottom of the planter to prevent the soil from leaching out.

Some of the materials you could use include rocks, broken terracotta pot pieces, broken concrete blocks, Styrofoam peanuts, plastic mesh, burlap, newspaper, landscape fabric, or weed protection sheets.

You can place the rocks, terracotta or concrete block pieces, Styrofoam peanuts at the bottom of the planter before adding the potting soil.

For the materials that are sheets such as a plastic mesh or landscape fabric, you can cut them to the right size and lay them on the bottom of the planter.

Some materials such as newspapers or a metal mesh won’t last long as they get decomposed or degraded faster.

If you’re going to use materials such as rocks, pot, or concrete pieces, I suggest putting a layer of the plastic mesh or landscape fabric between the potting soil and them. 

This makes it easy when you want to reuse the potting soil for the new growing season. Otherwise, you’ll have to spend time removing the pieces from the potting soil.

What precautions to take before making drainage holes?

It’s best to use eye protection before you start drilling holes in materials with a power drill. A pair of protective gloves would also be useful especially if you’re going to use heat to make holes.

Wear a dust mask that will protect you from inhaling the particles flying around as you drill holes in the material.

I would also suggest keeping some old cloth or tissues to help you clean the mess it may create as you drill.

Keep some material such as burlap, landscape fabric, tarp, plastic sheet, or newspaper below the planter. This will help secure the planter while drilling as well as collect any debris falling out.

How to make drainage holes in plastic pots?

Plastic is probably the easiest material to make drainage holes in. Plastic pots you buy at nurseries or garden centers may come with markings that already contain drainage holes.

You just need to use a sharp object like a screwdriver to poke on those markings and bring out the drainage holes.

If the plastic planters don’t already contain such drainage holes, you can drill some using a screwdriver or a power drill.

Make sure to mark the locations on the bottom of the planter where you want the drainage holes. You can do this using a pencil. You can heat the screwdriver and melt holes through the planter at the marked locations.

If you’re going to use a drill, place the pot on a stable surface so the bottom is facing you. You can place a tarp, plastic sheet, or newspaper underneath so it is easier to clean the fallen plastic debris.

Hold the drill straight on top of the marked spot and start making a hole at a slow speed. Make sure to hold the planter with one hand so it does not move. Gently push the drill so it keeps digging a hole in the plastic. 

You can stop and keep adding a little water in between to cool off the drill. This helps if the plastic is very thick.

Once you have drilled all the holes, you can clean them up to remove any unwanted plastic.

How to make drainage holes in wooden pots?

Wood is another material that is easy to drill into. There may already be drainage holes in wooden pots you buy at a garden center.

You can use a power drill to drill drainage holes in the plastic planters. You can mark the locations of the drainage holes on the bottom of the planter using a pencil.

Put the pot on a stable surface so the bottom is facing you. It is easier to clean fallen wood debris if you place a tarp, plastic sheet, or newspaper beneath it.

To start making a hole, hold the drill straight on top of the marked spot. To prevent the planter from moving, hold it with one hand. Put the drill in motion so it can dig a hole. 

You can cool off the drill by stopping and adding water. This is useful if the wood is thick. You can clean up the holes once you’ve drilled them.

How to make drainage holes in ceramic pots?

It can be tough to make drainage holes in a ceramic or terracotta pot. Not just because the material is dense but it is also brittle. If you’re not careful you can break the planter.

The method is the same as you would with a wooden planter. You need to use a power drill and a diamond drill bit to make the drainage holes. But you need to stick some artist tape on the marked spots before doing that.

This will help “soften” the blow of the drill on the ceramic so it doesn’t crack as easily. I would also suggest using the drill slow and steady so you’re super careful with it.

Put the pot on a stable surface so you can access the bottom. Use one hand to hold the planter steady as you drill holes in it.

Place the drill bit at a 45-degree angle when you start. Start the drill slowly and put gentle pressure on it. This will help it drill a hole in the material. Once it starts to cut a hole slowly move the drill bit so it is straight over the planter.

You should stop after a little bit has been drilled. Then pour some water on the drill bit and hole to cool them off. And then you can start drilling again. Keep doing this till a complete hole has been drilled.

How to make drainage holes in fiberglass pots?

It’s best to use a steel drill bit to make holes in fiberglass pots. The process will be the same as other materials. But it’s best to drill from the interior unlike the other materials.

Keep the fiberglass planter on a raised surface so it remains off the ground. You can keep a tarp or plastic sheet at the bottom to collect dust and debris.

Mark the drill locations on the inside of the planter using a pencil or marker. Use one hand to hold the planter stead as you place the drill on the marked position.

Place the drill bit right on top of the marked position and start the drill slowly. Put a little pressure so the drill bit starts cutting through the fiberglass.

It’s good if you stop after some drilling and put water on the drilled location. This helps clear the area as well as cool off the drill bit and prevent overheating.

Keep using the drill at the location till a clean hole has been drilled through the fiberglass material.

How to make drainage holes in metal pots?

You don’t have the problem of a metal pot breaking during the drilling. But it can be tough to drill the hole if the metal sheet is thick.

You can use a diamond drill bit for drilling holes in a metal pot as well. The process is similar to what you followed for a terracotta pot. I would also suggest using the drill slow and steady so you’re super careful with it.

Put the pot on a stable surface so you can access the bottom. Make sure there are no inflammable materials around as sparks could be created when drilling through metal. Use one hand to hold the planter steady as you drill holes in it.

Place the drill bit at a 45-degree angle when you start. Start the drill slowly and put gentle pressure on it. This will help it drill a hole in the material. Once it starts to cut a hole slowly move the drill bit so it is straight over the planter.

You should stop after a little bit has been drilled. Then pour some water on the drill bit and hole to cool them off. And then you can start drilling again. Keep doing this till a complete hole has been drilled.