Go shopping for absorbent underwear and you will be handed a number within about four seconds. 15ml. 50ml. 90ml. 200ml if somebody is feeling ambitious.
Nobody tells you what any of it means. You are expected to look at "50ml" and somehow know whether that covers a Tuesday.
So here is the translation. What a millilitre of urine actually looks like, how to work out your own number in about ten minutes with a set of kitchen scales, and why the biggest number on the shelf is almost never the right one to buy.
What absorbent underwear is
Absorbent underwear is normal looking underwear with an absorbent panel built into it. The panel wicks liquid away from the skin, holds it in a core, and sits behind a waterproof barrier so nothing reaches your trousers. You wash it and wear it again.
That is the whole idea. It replaces the pad, rather than holding one. If you want the longer version of how the layers work, we covered it in what to know before buying leakproof underwear for men. This piece is about the number on the label.
What a millilitre of urine actually looks like
Millilitres are meaningless until you put them next to something you have held. So:
- 1ml is a large drop. Roughly what lands on the floor when you flick a wet hand.
- 5ml is a teaspoon.
- 15ml is a tablespoon. This is roughly the territory of a decent post void dribble, the one that arrives two minutes after you have zipped up and walked off.
- 25ml is a single pub measure of spirits.
- 50ml is a double, or one of those small hotel bottles. Ten teaspoons.
- 125ml is a small glass of wine.
- 300 to 400ml is a normal, comfortable trip to the loo.
That last one is the useful bit of perspective. A full bladder release is several hundred millilitres. Absorbent underwear is built for the gap between a drop and a glass of wine, and that gap covers the overwhelming majority of men who need it.
How much do you actually leak? The ten minute version
Most men guess. Most men guess badly, in both directions, because a damp patch feels enormous and a dry morning feels like proof there is no problem.
There is a proper way to find out, and clinicians have used it for decades. It is called a pad test, and the home version needs nothing but kitchen scales.
Urine is close enough to water that one gram equals one millilitre. So:
- Weigh a dry pair of underwear, or a dry pad, in grams. Write it down.
- Wear it through a normal day. Not a careful day. A normal one, with the coffee and the commute and the walk to the car park.
- Weigh it again at the end.
- Subtract. The difference in grams is roughly the millilitres you leaked.
The International Continence Society grades a 24 hour version of this test as mild at 4 to 20g, moderate at 21 to 74g, and severe above 75g. Compare your own number against that and you will have a far better idea of where you sit than any amount of guessing.
Do it twice, on two different days. One heavy gym session or one long drive can skew a single reading badly, and it is worth knowing whether your leaks are a daily baseline or a situational spike. If the number is climbing over months, or comes with a weak stream, pain or blood, that is a GP conversation, not an underwear one.
But lets be honest this is probably overkill.
Matching the number to your day
Once you have a figure, the shopping gets simple.
- Up to about 15ml. Drops after the loo. The odd one during a lift or a cough. You are not changing anything mid day, you just want the last drop caught. This is the biggest group by a distance.
- Up to about 50ml. Small leaks arriving on and off through the day. Urgency you do not always beat. Long meetings, long journeys, long queues. You want one pair to hold the whole day without you thinking about it.
- More than 50ml, or unpredictable. Recovery after prostate surgery, a bad flare, or a day where you genuinely cannot predict what is coming. What you need here is not one enormous pair, it is the ability to change the absorbent part without changing your underwear in a service station toilet.
That last distinction is the one the industry keeps missing. Above a certain point, capacity is not the answer. Swappability is.
Why the biggest number is the wrong default
The instinct is to buy maximum absorbency and stop worrying. It backfires, for four reasons.
Bulk. Capacity comes from material. More capacity means a thicker panel, and a thicker panel is exactly the thing that makes underwear announce itself through chinos. The whole point of getting away from pads was to stop looking like you are wearing one. We went into this properly in the importance of discreet design.
Drying time. A heavy core takes longer to dry, which means you need more pairs in rotation to cover the same week. You have bought more product to solve a problem you did not have.
Comfort. A panel sized for 200ml sits differently against the body than one sized for 15ml. It is warmer, stiffer and more noticeable, all day, whether or not you ever use the capacity.
False confidence. Rated capacity is a laboratory figure measured lying flat. Real life happens sitting down, and sitting down puts pressure on a saturated core. This is the number nobody advertises: how much liquid stays put under compression. A well engineered 50ml panel that holds under pressure will outperform a cheap 90ml one that gives some of it back the moment you get into the car.
The three numbers that matter more than capacity
Capacity is the number on the box. These three decide whether you actually stay dry.
Speed. How fast the panel pulls liquid off the skin. A slow panel with a big core still leaves you sitting in it for a few seconds, and those few seconds are what you notice.
Retention under pressure. Covered above, and worth repeating because it is the single biggest difference between good absorbent underwear and bad.
Capacity after fifty washes. Absorbent cores degrade. Fabric softener is the main culprit, because it coats fibres and stops them taking on liquid, which is why the care label on any decent pair tells you to skip it. Line dry rather than tumble dry and wash at 30 to 40 degrees and a good pair will still be performing years in.
One more thing, and it catches almost everyone out: absorbent underwear does not reach its rated capacity straight out of the packet. The fibres need a wash to open up. Wash before first wear, every time, or you will test your new pants on day one and quietly conclude they do not work.
Where Frank's Pants sit on the scale
All three look like normal underwear. The only difference is how much they hold.
- The Active, £20. Around 15ml. Built for the last drop and post loo dribbles.
- The Everyday, £22. Up to 50ml. Built for small leaks arriving on and off through the day, and for the dashes you only just win.
- The Ultra, £27. Three washable clip in pads, each holding up to 50ml. Built for days you cannot predict, where changing the pad beats changing the pants.
All of it is washable, reusable and designed to be forgotten about, which as we found when we put disposables and reusables side by side is where the real difference shows up over a year. The full breakdown of how the layers work is on our technology page.
And if the number you measured surprised you, absorbent underwear is the floor rather than the ceiling. It handles the consequence while you work on the cause, and the cause is often more fixable than men assume. Start with pelvic floor exercises for men, then how to stop bladder leaks in men.
Every pair comes with Frank's Word, our 60 day risk free guarantee. Wear them, wash them, live in them. If they do not keep you dry, we refund you in full and you keep the pants.
Frequently asked questions
What is absorbent underwear?
Absorbent underwear is reusable underwear with an absorbent panel built into the fabric. The panel wicks liquid away from the skin, holds it in a core and sits behind a waterproof barrier, so bladder leaks are contained without a separate pad. It is machine washable and worn like ordinary underwear.
How much does absorbent underwear hold?
Most men's absorbent underwear holds between 15ml and 90ml. For reference, 15ml is a tablespoon and 50ml is ten teaspoons. Frank's Pants range from around 15ml in The Active to 50ml in The Everyday, with The Ultra using three swappable 50ml pads.
How do I know what absorbency I need?
Weigh a dry pair of underwear in grams, wear it for a normal day, then weigh it again. One gram is roughly one millilitre, so the difference tells you how much you leak. Repeat on a second day, as a single reading can be skewed by an unusually heavy or light day.
Is more absorbency always better?
No. Higher capacity means a thicker panel, longer drying time and more bulk under clothing, and rated capacity is measured flat rather than under the pressure of sitting down. Matching absorbency to your actual leak volume gives better comfort and better real world performance than buying the highest number available.
Does absorbent underwear smell?
Well made absorbent underwear locks liquid into the core and away from the air, which is what causes odour. Wash at 30 to 40 degrees, skip fabric softener, and line dry rather than tumble dry, and it stays fresh. Fabric softener is the common culprit when odour or reduced absorbency creeps in.
Do I need to wash absorbent underwear before wearing it?
Yes. Absorbent fibres do not reach full capacity until they have been through a wash cycle. Always wash before first wear, or the first day of use will not reflect what the underwear can actually do.