How Many Pees can a Diaper Hold? Real Experiment!

Introduction

As a Dad, I've spent a lot of time changing diapers. But even though I have a lot of experience changing diapers, I couldn't answer the question "How many pees can a diaper hold?" accurately.

I researched for hours online, and I couldn't find a single reliable source. So... I decided to run my own experiment. It's science time!

These are the steps I took to answer the question

Step 1. I bought diapers of all sizes (and brands) and completely filled them up. They hold a lot more liquid than you may think! Read more.

Step 2. I researched how much pee a baby's bladder can hold based on their age. And how much they fill it before they pee. Read more.

Step 3. I did the math and came up with a definitive and scientific answer to how many pees a diaper can hold! Read more.

TL;DR

Theoretically a diaper can hold between 4 and 9 pees (regardless of the size). But in real life, a diaper can only hold between 3 and 7 pees. With an average of 4 and a half pees per diaper.

But I would encourage you to read the whole post, because I did some pretty nice finding along the way!

Or watch the video here:

Step 1: How much liquid can a Diaper Hold?

The first question is pretty straight forward. I had to find out how much pee a diaper can hold. So I bought 5 different diaper sizes for all different ages and filled them up a little at a time. I came up with the following results:

How Much Liquid can a Diaper Hold? (In Theory)

Diaper Size	For Babies weighing	In Theory holds
Size 2	3 to 6 kg (6.6 to 13.2 pounds)	168ml (5,7 oz)
Size 3	6 to 9 kg (13.2 to 19.8 pounds)	278ml (9,4 oz)
Size 4	9 to 15 kg (19.8 to 33 pounds)	502ml (17 oz)
Size 5	15 to 20 kg (33 to 44 pounds)	591ml (20 oz)
Size 6	20 kg and up (44 pounds and up)	769ml (26 oz)

But that didn't seem good enough to me... because as a Dad, I know that sometimes a diaper doesn't have to be completely full for the pee to come out. This is specially true during the night, because only one side of the diaper tends to be completely filled.

Hence, I completed this step with a little help from my 4 month old daughter (size 3 diaper) and my 18 months old son (size 5 diaper, he's huge!).

As a Dad I know that sometimes a diaper doesn't have to be completely full for the pee to come out.

I weigheted their diapers for a week, and found out that every time a diaper reached 75% of it's capacity, the pee would come out. This number turned out to be extremely consistent both for my son and my daughter. So, the amount of liquid that a diaper can hold changed in real life.

When a diaper has reached 75% of it's theoretical holding capacity, it no longer serves its purpose.

How Much Liquid can a Diaper Hold? (In Real Life)

Diaper Size	For Babies weighing	In Theory holds	In Real Life holds
Size 2	6.6 to 13.2 pounds	168ml (5,7 oz)	126ml (4.2 oz)
Size 3	13.2 to 19.8 pounds	278ml (9,4 oz)	208.5ml (7 oz)
Size 4	19.8 to 33 pounds	502ml (17 oz)	376.5ml (12.7 oz)
Size 5	33 to 44 pounds	591ml (20 oz)	443ml (15 oz)
Size 6	44 pounds and up	769ml (26 oz)	576ml (19.5 oz)

Interesting to know!

Does a more expensive diaper hold more pee?

I found this extremely interesting, and I'll publish my findings in a post next week, but this is a preview of what I found:
Different brands of diaper do hold different amount of liquid, but the differences are extremely slim. Not enough to compromise this experiment, let alone to justify the difference in price.
The interesting part is... depending on how I filled the diapers, the results were different! If you drown the diaper, one brand comes on top and holds consistently more liquid than the others. But if you pour a little liquid slowly, another brand comes on top. If you pour liquid fast... another brand comes on top! That's why diaper companies can safely say that their diaper holds more pee. Because it depends on the way you fill them up! Snicky, isn't it?

Step 2: How much do Babies Pee?

I researched for hours, read over a dozen scientific papers describing how much both adults and babies should pee... and couldn't find a definitive answer to this question.

Why?

Because the amount of daily pee depends on multiple things like how much you drink, how much you sweat, etc. Even genetics play a crucial role. Everyone is different, and we all produce different amounts of pee every day.

But! There's one thing that is actually pretty consistant among us: bladder size.

When the bladder has reached 50% of it's capacity, it signals our brain that it's time to pee. As adults, we can hold the pee for some time. But babies pee the very moment their bladder reaches 50% of it's capacity.

So... if we could find out the bladder size of a baby, we could know how many ml (or oz) of liquid per pee they're producing.

I started reserching again and I found this interesting paper published in the National Library of Medicine titled Estimating normal bladder capacity in children. In their research, doctor David Zurakowski, professor at Harvard Medical School found out that bladder size can be determined by 2 practical linear formulas:

"2 x age (years) + 2 = capacity (ounces) for children less than 2 years old, and age (years) divided by 2 + 6 = capacity (ounces) for those 2 years old or older."

But don't worry. I'll save you the time, and I'll do the math myself in the next step!

Step 3: Doing the Math!

The third step meant putting my findings together and this is what I came up with. Note that I had to use data from Paul Young, M.D.. (a pediatrician at babycenter.com) to get the average weight based on age.

These were the final results:

Age (months or years)	Pounds (average boys and girls)	Bladder size (ounces)	Pee size (ounces)	Number of Pees Diaper Holds (Theoretically)	Number of Pees Diaper Holds (In Real Life)
1	9,59	2,17	1,08	5,26	3,88
2	11,79	2,33	1,17	4,89	3,60
3	13,45	2,50	1,25	4,56	3,36
4	14,77	2,67	1,33	7,05	5,25
5	15,87	2,83	1,42	6,64	4,94
6	16,76	3,00	1,50	6,27	4,67
7	17,53	3,17	1,58	5,94	4,42
8	18,19	3,33	1,67	5,64	4,20
9	18,85	3,50	1,75	5,37	4,00
10	19,51	3,67	1,83	5,13	3,82
11	19,95	3,83	1,92	8,87	6,63
12	20,39	4,00	2,00	8,50	6,35
15	21,94	4,50	2,25	7,56	5,64
18	23,26	5,00	2,50	6,80	5,08
21	24,69	5,50	2,75	6,18	4,62
22	25,24	5,67	2,83	6,00	4,48
23	25,68	5,83	2,92	5,83	4,35
2	27,34	7,00	3,50	4,86	3,63
2,5	29,32	7,25	3,63	4,69	3,50
3	31,20	7,50	3,75	4,53	3,39
3,5	33,29	7,75	3,88	5,16	3,87
4	35,49	8,00	4,00	5,00	3,75

Conclusion:

As you can see from the above table, theoretically a diaper can hold between 4 and 9 pees. But in real life, a diaper can only hold between 3 and 7 pees. With an average of 4 and a half pees per diaper. This is fairly true for all sizes, because the bigger the diaper, the bigger the child, and the bigger the pee.

Posted in: Baby Diaper Experiment