Scientists reveal how to pick out the cleanest cubicle in ANY public toilet (and why it is different for men and women)

It’s a familiar puzzle that many of us face on an almost daily basis.

When nature calls and your only option is a public toilet, which cubicle should you pick? 

Thankfully, science now has the answer as researchers have revealed how to always choose the right cubicle in any public toilet. 

When it comes to finding the most germ-free loo, the trick is to choose the one that is used the least frequently.

What makes this so tricky is that everyone else in the bathroom is trying to do the exact same thing.

Psychologists have shown that humans have a natural preference for the middle choice, even if they’re not aware of it.

That means making a dash for the toilets at the far end of the row could help you avoid any unpleasant surprises left by the previous occupants.

So, whether you’re using the men’s bogs, the women’s loos, or simply heading for the urinals, here’s how to pick out the cleanest cubicle every time. 

How to pick the right cubicle with science

In most public bathrooms, it’s usually pretty obvious which of the cubicles are clean and which are dirty.

Likewise, you might generally find yourself choosing between whichever toilets are left unoccupied.

In those cases, your choice is fairly easy, but the choice becomes much harder when faced with otherwise identical options.

Suppose you walk into the bathroom and find three identical stalls, none obviously cleaner than any of the others – which should you choose?

The answer is to pick the cubicle which is the least likely to have been chosen by anyone else in that same situation since that toilet will have been used fewer times since its last clean.

Research in this area generally shows that people have a preference for the middle toilet and so these should be avoided where possible.

In an influential 1995 study, a psychologist from UC San Diego looked at how four identical stalls were used at a men’s bathroom at a California state beach.

By measuring the amount of toilet paper that needed replacing over 10 weeks, the researchers could see which of the stalls was the most popular.

Of the 86 rolls that were finished, only 40 per cent came from the outer two toilets – far less than the 50 per cent that would be expected if people chose by chance.

This suggests that people have what psychologists call a ‘centre bias’ for toilet cubicles – meaning they prefer the middle option when all other things are equal.

However, that still leaves you with two toilets to choose from: one on the nearside closer to the door and one further away.

This is where it will make a difference whether you are a man or a women.

A survey of toilet use habits suggests that men tend to prefer the cubicle closest to the door while women tend to gravitate away from it.

If you’re looking for the least used, and therefore cleanest cubicle this means that men should go for the option furthest from the door and women should go for the closer option.

However, there are still a few exceptions to this rule that are worth bearing in mind.

Flushing the toilet sends a plume of tiny water droplets up into the air surrounding it. This is an aerosolized cloud of bacteria and faecal matter which can build up on surfaces around the toilet 

Unlike in these examples, cubicles aren’t always exactly identical and some offer a bit more privacy than others.

Dr Thomas Heston, associate professor of medicine at Washington State University, told MailOnline that understanding this can help you choose the cleanest loo.

Dr Heston conducted a study on a row of three toilets where the right end met a solid wall while the left end was only separated from the common bathroom space by an exposed partition.

Of the 37 times that at least one stall was occupied, the stall on the far left closest to the wall was occupied 62 per cent of the time.

Meanwhile, the stall on the far right, which didn’t have a solid wall, and the centre stall were only used about a quarter of the time each.

Dr Heston says: ‘I suspect that when in a vulnerable, private situation, there is a tendency to use a stall perceived as most private and secure.

‘A stall that is adjacent on only one side to another stall would be both most private and perceived to be most secure. Thus, I hypothesize that these stalls would be used most frequently.

‘Stalls in the middle, or where one side faced the open room, would be least private and thus used less frequently.’

To get the cleanest toilet, men should choose the cubicle furthest from the entrance while women should go for the one closest to the door (file photo)

So, if there is one option that seems extremely private and secure, the most hygienic option is actually to choose the less favourable position on the end or in the middle.

Does it matter which toilet you choose?

Although it might seem like fussiness or germaphobia, there are real health reasons to try and pick a cleaner cubicle.

Whenever a toilet is flushed, something called a ‘toilet plume’ ejects a cloud of aerosolized faecal matter, toilet, water, and bacteria which coats every surface.

Elizabeth Paddy, a doctoral researcher on toilet plumes from Loughborough University, told MailOnline: ‘Flushing generates rapid, turbulent water movement in the toilet bowl that aerosolizes droplets containing bacteria from faecal matter and other contaminants.

‘Some of these droplets quickly settle onto nearby surfaces such as the flush handle, sink, and doorknobs, while others remain airborne for extended periods, where they can be inhaled by other bathroom users.’

These aerosols are at their most concentrated in the first five minutes after flushing which can become a real problem in poorly ventilated and busy public bathrooms.

When a toilet is used too frequently without cleaning in between, Ms Paddy says this can lead to ‘significant accumulation and survival of bacterial bioaerosols.’

Flushing a toilet releases a cloud of particles which can spread up to five feet in the air. Using lasers this image shows the cloud of toilet water, bacteria, and faecal matter rising from the bowl. Choosing a less frequently flushed toilet could help you avoid these particles

If any of the people using the bathroom before you were sick, this coating of toilet material can pass on their illness to you.

Thankfully, some studies suggest that it should be possible to reduce the risk of catching a disease by picking a less frequently used toilet.

Dr Thomas Heston adds: ‘Proper hand washing is the most important way to prevent disease transmission.

‘However, it is theoretically possible to reduce disease transmission further by utilizing less frequently used stalls.’

In addition to choosing the least popular stall, you can also try and avoid features which encourage the buildup of bioaerosols.

Research suggests that lidless toilets produce a bigger flume than toilets with closing lids, so try to avoid any options with these.

Likewise, Ms Paddy points out that good ventilation from a window or fan usually means that fewer aerosols have a chance to settle.

She says: ‘While it can be challenging to determine by appearance alone, stalls equipped with touchless features in bathrooms with effective ventilation are likely to have lower bioaerosol concentrations.’

How to pick the right urinal

However, when it comes to urinal etiquette, the situation is a little bit different.

Since men don’t touch any surfaces while using a urinal, privacy rather than hygiene is the biggest issue.

And for a surprising number of men, this factor can actually be the difference between using the urinal or having to wait for a less hygienic stall.

Approximately a quarter of men experience a condition called Paruresis, more commonly known as shy bladder.

In one 2023 study, 35 per cent of university students said they avoided an available urinal due to anxiety related to being around others.

So, the question is: faced with an open row of urinals, which should a man choose to maximise the amount of time before someone stands next to him?

Thankfully, mathematicians have actually created a formula which proves that there is an answer to this question.

To maximise the time at the urinal before someone stands next to you, men should always choose the urinals at the far end of the row. Based on mathematical modelling, these choices should give the greatest amount of privacy (file photo)

By modelling different ‘strategies’ men might use to choose a urinal, such as choosing the furthest from the next man or picking at random, these calculations show that the end choice is always best.

To maximise your privacy, you should always pick the urinal at the end furthest from the door if it is available and the one next to it is unoccupied.

If that isn’t available, the end closest to the door is also a good choice except for the case in which toilet users are simply choosing the closest urinal without any regard for others’ privacy.

If neither is available, then the next best option is simply whichever urinal has the most space on either side of it.