How to Choose Period Pants: Flow, Style, Size & Lifestyle

How do you choose period pants?

Start with your flow, then your style, then your size, and let your lifestyle tune the final choice. It’s easy to do this backwards: fall for a lacy cut, order your usual dress size and only then wonder whether it’ll cope with day two.

Flow first, because absorbency is the thing you can’t fix after the fact. A pair that’s too light leaks; a pair that’s far too heavy feels bulky on a light day and costs more than it needs to. Style second, because you’ll only wear pants you like the look and feel of. Size third, because a gusset that’s slipped out of place leaks whatever its absorbency. Lifestyle last, because it changes the balance between the first three.

What absorbency do you need?

Most brands grade their pants in four levels, and the number of tampons or pads you get through on your heaviest day tells you where to start. Annahitah’s levels are Light, Medium, Heavy and Super Heavy. Its Super Heavy styles hold six to eight tampons’ worth; its Heavy and Medium styles are described as saving three to five tampons per wear; its Light styles carry no figure.

A rough translation from your current habit:

Other brands publish ml figures alongside their levels. Brand A, for instance, quotes up to 20 ml for Light, 30 ml for Moderate and 50 ml for Super, based on a 5 ml tampon, and Brand B puts Heavy at 20 to 30 ml. Those are lab capacity numbers, not promises about how long a pair lasts on your body, and Annahitah doesn’t publish ml at all. The point here is to pick the level that matches your worst day, because a Heavy pair works fine on a light day but not the other way round.

How does your flow change across your period?

Bleeding is heaviest in the first two days and tails off from there, so most people need two absorbency levels, not one. The NHS says a period lasts about five days on average (anywhere from two to seven), with the heaviest bleeding at the start and the colour shifting from red to pink or brown as it lightens.

That pattern shapes your shopping list. Days one and two want your heaviest level, and probably a fresh pair for the night. From day three, a level down is often enough, and the last day or two can be a Light pair that feels like ordinary knickers.

If your heaviest day means changing a pad or tampon every hour or two, passing clots bigger than a 10p coin, bleeding through to clothes or bedding, or periods that run past seven days, the NHS lists those as signs of heavy menstrual bleeding and suggests talking to your GP, particularly if it’s affecting your life or comes with severe pain. Super Heavy pants can help you manage it, but they shouldn’t stop you asking the question.

Which style suits your day?

Briefs and high-waists give the most coverage, thongs and seamless cuts disappear under tight clothes, and the best style is the one you’d reach for on a normal day. Brand C’s advice is the same: buy the cut you already wear. A period pant you find frumpy stays in the drawer.

Annahitah’s twelve styles sort into these shapes:

Two practical points. Coverage matters more than it looks: Brand D notes that pants with absorbency running to the front and back waistband hold up better for heavy flow than gusset-only designs, and absorbency that reaches the back is what you want for sleeping. And all three of Annahitah’s thongs sit in the Light collection, so a thong is a light-day or backup choice, not a day-two choice.

Does fabric change the choice?

Yes, because the feel against your skin is what you notice all day. Annahitah’s range runs from organic cotton (Valentina, Lilah, Venus, Eden) to bamboo (Serendipity, Gaia) to nylon and elastane blends (Shanti, Odessa, Athena, Aurora, Luna, Nirvana); the site says its range includes recycled nylon. Cotton and bamboo feel soft and matte; nylon blends feel smooth and stretch more, which is partly why five of the seven Seamless styles are nylon blends. If you know you prefer one in ordinary knickers, you’ll prefer it here.

How do you get the size right?

Measure your hips at the widest point and your waist midway between your lowest rib and hip bone, then read both against the brand’s chart in centimetres. Dress size alone is a rough guide because brands cut differently, and Which? makes the same point: check the hip measurements, because ranges vary widely between brands.

Annahitah’s adult sizes run from XXS (UK 4-6, hips 84-88 cm) to XXL (UK 16-18, hips 114-118 cm), with a teen chart starting at XXXS (UK 2-4, hips 79-83 cm). The site describes its sizing as on the generous side and says to pick the smaller size if you’re between two. That’s the opposite of some brands, so don’t carry a sizing habit across from elsewhere.

Fit affects leaks more than people expect. Too big and the gusset sags away from your body; too tight and moisture wicks out at the seams. We cover the full tables and the measuring method in our size guide.

What should sport, sleep, work and school change about your choice?

Each setting shifts the balance between coverage, discretion and how long you’ll go before you can change. Flow level stays the starting point; what moves is the cut and how many pairs you carry.

• Sport and the gym. Seamless and thong styles vanish under leggings, and sweat-wicking matters as much as blood. Annahitah’s Sweat Control collection (Odessa, Venus, Nirvana, Luna, Eden) is built for this, with Odessa as the Super Heavy option when you’re training on a heavy day.
• Sleep. You want your heaviest level, worn fresh at bedtime, with coverage that reaches up the back. Annahitah says its Super Heavy styles are designed for overnight protection and suggests switching to a second Super Heavy pair for the night on a super heavy day.
• Work and long days out. Pick the level above what you’d choose at home, because you can’t always change. The organic cotton Eco-bag that comes with every order holds a spare or a used pair.
• School. Teens want something that feels like normal knickers and lasts the school day without a change. Annahitah’s Teenage collection (Valentina, Athena, Shanti, Lilah, Serendipity, Odessa) covers Heavy and Super Heavy, and Valentina is the only style sold in XXXS.
• Bladder leaks, postpartum and perimenopause. Annahitah groups styles for each on its site, and the same four steps apply. For postpartum bleeding and endometriosis the site points to Shanti and Odessa; for unpredictable perimenopause flow a mix of levels makes sense.

Which period pants should a beginner buy first?

Buy three pairs at the level that matches your heaviest day, try the first one at home, and add lighter pairs once you know your pattern. That’s the advice that holds across brands: Brand E says start with your heaviest day’s level, Moral Fibres says trial at home first, and Brand C suggests three heavy pairs to begin and six or seven to switch fully.

Heavy first because a Heavy or Super Heavy pair works on every day of your period, while a Light pair works on two of them. Starting heavy means your first wear is a success, and a leak on the first wear is what puts people off.

At home first because, as Brand D puts it, you want to learn how a pair feels as it fills and when you’d want to change before you trust it on a train. For a first period, the NHS says period underwear is safe to use and that pads may be the simplest place to begin; Brand C’s teen guidance suggests Medium for a first period and Heavy for heavier days.

Across Annahitah’s range, the four steps point to these rows:

Once you’ve found your row, the collection pages are grouped the same way. If your heaviest day is light, start with light flow pants. If a regular tampon sees you through a few hours, medium flow pants are the match. If you change often or use super tampons, go to heavy flow pants. And if you soak through, double up or need overnight cover, start with super heavy flow pants.

How many pairs do you need?

Three to five pairs cover a whole cycle for most people, as long as you wash a pair or two part-way through. That’s Annahitah’s own guidance. Brand C suggests three heavy pairs to begin and six or seven to switch fully, and Moral Fibres puts full-time use at about six. Anyone who changes twice on their worst days, or has nowhere to dry pants indoors, should plan for more.

What else should you check before buying?

Materials, chemical policy, returns and the brand’s own honesty are what separate pants that look identical in a photo. Four checks:

• Silver. Which? found silver antimicrobials in seven of 12 UK brands it tested in 2023 and called them unnecessary. Annahitah’s pants are silver-free; its antimicrobial styles use a certified agent with no silver, and six styles have no antimicrobial finish at all.
• Certifications. Ask whether the materials come from OEKO-TEX and GOTS certified suppliers (Annahitah’s do) and what the brand will say about PFAS testing. OEKO-TEX doesn’t certify anything as PFAS-free, so be wary of brands that claim it outright.
• Returns. Annahitah accepts unworn pants back within 30 days for a refund or exchange, which covers a wrong size. Check the policy anywhere you shop, because you can’t return worn pants.
• Lifespan. Annahitah quotes 18 months to three years with the right care. Ask any brand the same question before you compare prices.

What mistakes do first-time buyers make?

Buying too light, buying one level for every day, and sizing from a dress label are the three to avoid. Brand B describes the first two neatly: too light brings leak anxiety, too heavy brings bulk on days you don’t need it. The fix for both is owning two levels.

The fourth mistake is expecting a period pant to behave like a pad you forget about. It’s underwear. It fits like underwear, and it fills over hours. Once you’ve worn one through a heavy day at home you’ll know your own change point, and the whole choosing exercise gets much easier the second time.