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Large open rounded entrance hole on nest box fixed to tree

Robin nest box hole size

No need to be so precise when it comes to selecting a robin nest box hole size, it can vary in size so is universal, but I do have my own recommendations.

Robin nest box hole size in my mind would have a smaller than usual 100mm tall entrance hole. Width to correspond to this height would be 300mm as it appears more fitting, yet is still a small size overall. Robin bird box entrance hole sizes are similar in square or rectangular shape holes, but other shapes vary hugely.

Most common garden birds that nest in our bird boxes we buy do so in a small, rounded hole size in most circumstances, but this changes with a robin.

Robins like to nest in a bird box with a large open front, while large it may be I like to be more cautious with a smaller nest box hole size.

Hole size of course would preferably match up to the robin nest box size, which is often an important component in the design.

I like to keep it to a minimum if building a robin nest box, so make it only 100mm high if you can, with a 300mm width.

To buy a robin bird box can be much larger, but that is related to the design of the box as it can use a triangle or rounded hole shape.

Bird boxes for robins can vary in size or shape, so this can change the hole size dramatically, but all robin nest boxes would look similar - in that it uses a large opening.

100mm minimum height

Really, there's no hard or fast rules when it comes to the exact measurements of a robin nest box hole size, it can vary greatly depending who has built it.

Its safe to say then robins do use your bird boxes of any kind, so they may be willing to occupy your own one regardless of any potential design flaws.

What dimensions you need to consider most when buying or building your own bird box is a more important entrance hole height, over the width.

I would say you'll be in good hands in offering up a entrance hole that is up to 100mm tall, as a minimum height only.

It could be you go as high as 150mm or 200mm, but it can begin to be less appealing to potential nesters.

The best bird boxes for robins often use a vertical or horizontal rectangular shape, but all these measurements go out of the window when using a made in woven or bird box that uses a triangular hole.

Proof is in the pudding then, so as all these entrance holes are used, they must work.

300mm maximum width

Once again, to build or buy a robin bird box with a 100mm minimum entrance hole has little baring on successfully attracting robins to nest in your garden.

But so too does it not matter much how wide the robin bird box entrance hole is.

In fact you could use a ratio of triple that of the recommend height outlined above, but at this stage it can be a bird box - if built big enough - that could attract blackbirds... as they use the same open design.

Make it a 300mm maximum width entrance hole then but never go beyond this.

Robins like to nest in a small, yet open fronted nest box that doesn't open them up to danger - so a large opening can reveal eggs to predators, making it easy pickings.

Think of the 300mm width I recommend as an attractive ratio to the 100mm tall opening I believe is a reasonable size.

Rectangle or square hole shape

Of course, bird boxes come in all shapes and sizes, so too does the entrance hole that is not always square or rectangular.

Robin entrance hole bird box sizes could be much higher than I've mentioned, but never are they any wider. Robin hole sizes could be triangular but they could be more rustic if built into a genuine log bird box cut out of a tree trunk, with hole sizes varying.

More so, a Robin entrance hole could be shaped into a ceramic teapot or actually made into a woven nester - designed by wildlife experts.

Rectangle or square is the most common robin bird box hole size but do understand, if built any other way, its perfectly within reason.

What robin bird boxes do have in common is that entrance hole is far larger than those found on bird boxes for smaller birds, such as boxes made for Blue Tits.

Rounded hole still attractive

To consider a bird box for a robin it can indeed make use of a square or triangle hole with a hole size height of 100mm, with a little wiggle room to make it higher.

But what makes robin bird houses so different is that they more often nest in open fronted bird boxes that don't follow traditional handmade wooden bird box guidelines in entrance hole sizes or shapes.

While a robin bird box is always going to use a larger hole compared to other common garden birds who nest in bird boxes - you can still use a round hole.

Whenever a bird box uses a round hole I believe it looks far more attractive to any birds who wish to use it. All while a square or rectangular bird box feels too open - so I don't feel safe how exposed it is to people, predators and the elements.

Make use of a robin bird box using a rounded hole if you feel any of this could scare you.

So while the entrance hole is a few sizes up, it at least would make you feel more comfortable when location the box in your garden.

Front panel similar to entrance hole

If you wish to build a robin bird box yourself at home, then you can use this simple little trick to get the whole of front side measured up in proportion.

It is also a noticeable feature on many robins bird boxes you can buy I've noticed.

Basically, the height of the open front where robins enter and exit can usually correspond to the height of the panel sitting below it.

Be it a wooden, ceramic or woven robin bird box, I have found a correlation between the height of the bird box entrance hole size - to that panel that sits across and below it.

So if the entrance hole was 100mm, it could be the panel below is approximately 100mm. I would say this is never the intention but it is a trait I've noticed with designers of the boxes - knowing that a comparable height simply looks nicer on the finished product.

Panel that sits across the front of the bird box has its use to, as its not for decoration. It is where the robins begin to build their nest behind - so it offers a secure fit while nesting material eventually protrudes out of the bird box entrance hole.


Whether you are building it yourself or simply buying a robin bird box while researching what is the best nest box hole size to bring more success.

While there's never going to be a universal hole size everyone can work off, its going to vary from one manufacturer to the next - but robins don't seem to be fussed if the hole doesn't always measure up the same.

It is quite common then to see nest boxes for robins vary in height and width.

For me, an entrance hole size of 100mm tall is going to be a safe bet, as its not too big as to attract other species.

Whereas a 300mm ratio for the width of the hole is within reason, but this width is going to be the actual width of the entire nest box that it would correspond to.

No hard or fast rules mind as you could experiment with different bird box designs, so hole sizes can vary greatly on each box.

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