Geeking Science: Queuing Theory and Lavatories

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Lavatory Science

Why are there always queues for women’s bathrooms but not men? They got the same number of stalls, right? The same equipment? Do women just have smaller bladders and need to go more? And what’s up with that pair thing? You know, women going to the bathroom in pairs.

Answer – Science to the rescue.

Biology of the Bladder – Let’s start with bladder size. Size comparison can be tricky because the bladder is a stretchy bag varying in size from two to more than six inches long with a capacity to hold about three cups (24 ounces) of urine (Healthline). The body gives warning with the bag is about a quarter full. The amount a liquid is about the same for men and women, except when a woman is pregnant. Pregnancy prevents full expansion and signals the need to empty sooner.

Therefore the queues in the bathroom are not from women needing to go more.

Sociology of Public Bathrooms – Therefore sociological factors may be impacting. A lot of the “long lines” can be seen at retail establishments. Women tend to be the primary shoppers in the United States. With a disproportionate ratio in the retail environment, queues will be created if male and female bathrooms are created with the same amount of stalls.

Sociology of Additional Tasks – Raising the stakes higher, women disproportionately take children to the bathroom with them. These lengthen the queue beyond what a single small body would indicate because part of the process of a bathroom run with the child is teaching them the etiquette of public bathrooms as well as guiding the child into a better understanding of their body through constant questions like “Do you need to pee or poop? Can it wait?”

Finally, for the public environment, women are usually the ones changing the diapers. This crowds the bathroom further, interfering with the flow of people in and out.

But queues also occur where the ratio of men to women are more balanced, or even skew to male heavy. For example, restaurants and sports functions. The only time I’ve experienced no line and saw a long line for the men’s side was at a computer sale in a convention center where the ratio was eleven to one male to female (I counted the crowd because I had been amazed).

Mechanics – One of the verifiable differences between men and women during a bathroom run is disrobing. For urination, men only need to unzip, not drop, pants. They can keep things fairly private even with a public urinal as no clothing needs actual removal. Further advantages in time are created by the public urinal, which does not require entering a stall and closing a door. Each step takes times. Women need to walk further, turn around, close doors, then disrobe below the waist, and reverse all this for both defecation and urination.

Since healthy humans should urinate on average six times a day (with four to ten being well within normal depending on food intake and activity level) and defecate once per day (with three times a day to three times a week being normal range (Hansen 2018)), that mean only one in six times is a male doing the full stall dance (turn around, sit down, wipe) compared to a woman. Since a urination stall visit takes about one and a half minutes versus a urinal visit, which is just shy of a minute, a man urinating vs. a woman urinating time in process is about half again as long.

Mechanics of clothing in relation to the body and mechanics of architecture both increase toilet time for women.

Architecture – Speaking of the building itself, I’ve said a couple times “same number of stalls” implying same number of relief stations. The thing is, that actually isn’t the case. Most architecture plans set aside the same space for men and women bathroom. Since three urinals take the space of two stalls, most male bathrooms actually have more relief locations than women’s areas.

Tossing in the need for changing stations for infants, which only recently started being included in the men’s bathrooms, women have significantly less stations for the lavatory tasks while also needing half again more time.

Mathematics РSimple math indicates women need larger bathrooms than men. They need more space to have equal number of relief stations as well as needing more stations than men since the mechanics take longer. Using the same space model, the average bathroom wait is half-a-lifetime for a woman during heavy time use (like between panels at a convention) versus eleven seconds for a man. 

The science of queuing indicates changes need to be made. Men don’t like waiting outside the bathroom like a creep for their ladies, and women don’t like waiting in line when needing to pee.

Fixes need to be done. Potty parity is an actual political hot-potato (Wikipedia).

Geeking Science – Mathematics, Architecture, Biology, Mechanics, Politics. Bathrooms runs touch so much.

But how about that “woman in pairs” thing. Is it because of the line wait? I got a theory that I made into a flash last October – see Pairs. (10/29/2017)



Bladder & Bowel Community. “Urinary Frequency.” (undated) – last viewed 12/5/2019.

Dawe, TJ. “Why Women Have to Pee So Often.” Beams and Struts. (undated, maybe 2012 based on blog comment). – last viewed 12/5/2019.

Ghent University. “Researchers study lengths of restroom queues.” 2017 July 17. – last viewed 12/5/2019.

Hansen, Alexandra. “The ‘Three and Three’ Rule of Pooping Tells if You’re Normal or Not.” Vice. 2018 September 11. – last viewed 12/5/2019.

Healthline. “Bladder.” (undated) – last viewed 12/5/2019

Jones, Val. “The Bladder: Gender Differences & Problems Peeing.” edocamerica. 2017 May 5. – last viewed 12/5/2019

“Why do women pee more often than men?” Quora. (answers provided 2017) – last viewed 12/5/2019.

Wikipedia. “Potty parity.” – last viewed 12/5/2019.