The best period underwear, by flow and fit (2026)

How we chose.

We did not wear these. We compared what each brand and Amazon listing publishes: absorbency in tampon equivalents or milliliters, coverage, fabric, size range, care instructions and PFAS statements. We kept established brands with large review counts and checked that every product link goes to that exact listing. We could not include Modibodi on the shelf because it is not sold on Amazon in the US; it is covered in our Knix review. Our method is on how we review.

Knix Super Leakproof High Rise.

Knix publishes a clear absorbency ladder: Light at 1 to 3 regular tampons, Moderate at 2 to 4 super tampons, Heavy at 4 to 7 super tampons, and Ultra at 7 to 11 super tampons. The Super Leakproof line sits at Heavy. The high rise cut covers more than a bikini, and Knix sizes run XS to 4XL, one of the widest ranges in the category. Knix Super Leakproof on Amazon.

Thinx Breathable Hip Hugger.

Thinx made period underwear mainstream, and the hip hugger is its signature cut. Thinx says its period underwear holds up to 12 regular tampons' worth and protects for up to 12 hours, and that its products are not made or treated with PFAS. That tampon figure comes from Thinx's own test, so it is best compared with other Thinx pairs rather than with Knix numbers.

Thinx for All Everyday Comfort Brief.

Thinx's lower cost line, sold as a two pack, with the same headline absorbency claim as the main line. It is the easier way to build a rotation from a brand you know. The cut and color range is narrower than the main Thinx line.

Knix Super Leakproof Dream Short.

Most overnight leaks happen at the back, which is where a brief ends. The Dream Short covers front to back like a sleep short, at Knix's heavy level. It is warmer than a brief, which is the tradeoff.

Saalt Comfort Modal Brief.

From the cup brand, a heavy absorbency brief in soft modal. If synthetic fabrics feel clammy to you, modal is the softer choice. Modal can pill over time, so follow the care label closely.

Saalt Seamless Thong.

A light pair that replaces a liner or about 2 light tampons per the listing. It is the backup we would pair with a menstrual cup or disc, and it does not show lines under fitted clothes.

Bambody Period Underwear.

At the top of Amazon's period underwear best seller list when we checked, sold as a three pack in bamboo rayon. It is the easiest way to get a week's rotation in one order. Bambody describes absorbency in general terms rather than in tampons or milliliters, so it is best for light to moderate days until you know how it performs for you.

Hanes Comfort, Period. Underwear.

A three pack from a familiar basics brand, rated for moderate leaks with odor protection per the listing. It suits backup, the start and end of a period, and anyone who wants to try the format before spending more.

How absorbency is measured.

There is no single industry test for period underwear. Brands translate what a gusset holds into tampon equivalents or milliliters using their own methods, which is why Thinx's "up to 12 regular tampons" and Knix's "4 to 7 super tampons" cannot be compared directly. For reference, the FDA's tampon labeling standard rates a regular tampon at 6 to 9 grams of absorbency and a super at 9 to 12 grams.

A practical way to read the labels:

Level	What it is for	Examples here
Light	Spotting, discharge, cup or disc backup	Saalt Seamless Thong
Moderate	Start and end of a period, light days alone	Hanes Comfort, Period.
Heavy	A full day on moderate flow, pad replacement	Knix Super Leakproof, Thinx, Saalt Modal Brief
Overnight	Sleep, with back coverage	Knix Dream Short

If you regularly soak through a heavy pair or a pad in an hour or two, the NHS counts that as a sign of heavy periods worth raising with a clinician.

How leak proof underwear works.

Most period underwear has three or four layers in the gusset: a moisture wicking top layer against skin, an absorbent core that holds fluid, and a leak resistant barrier underneath. Some brands add an odor control treatment. The gusset size and how far it runs toward the waistband at the back decide how well it handles lying down. That is why the same brand's brief, high rise and short can carry the same rating but behave differently overnight.

PFAS in period underwear.

PFAS are a large class of long lasting chemicals that have been used for water and stain resistance. The EPA describes them as persistent in the environment and in the body. Period underwear came under scrutiny after testing and lawsuits raised questions about PFAS in some products, and brands responded with policies. Thinx now states its products are not made or treated with PFAS. Before you buy any brand, look for a published PFAS policy rather than a vague "non toxic" claim.

How to wash period underwear.

Brands agree on the basics. Rinse a worn pair in cold water until it runs clear. Machine wash cold with like colors, or hand wash. Skip fabric softener and bleach, which coat or break down the absorbent layers. Line dry; tumble drying shortens the life of the leak resistant layer. Thinx's own FAQ suggests replacing a pair after about 30 washes, so treat period underwear as a semi durable item rather than a forever one.

Which pair for which situation.

• You want to stop buying pads on most days. Two or three heavy pairs (Knix Super Leakproof or Thinx) plus a light pair for the end of your period.
• You use a cup, disc or tampons and want backup. The Saalt Seamless Thong or another light pair.
• You leak overnight. The Knix Dream Short.
• You are postpartum. Heavy or overnight pairs are comfortable for the weeks of bleeding after birth, when internal products are off limits until you are cleared. Our postpartum dryness page covers the other changes that follow.
• You want to swim. Regular period underwear is not built for water. See the best period swimwear.
• You also have light bladder leaks. Many period brands, Knix and Thinx included, sell separate bladder leak lines rated in milliliters.

Cost and waste over time.

A single pair costs more than a box of pads, but a rotation replaces disposables for many cycles, so the cost over time is lower for most people who wear them regularly. The waste difference is larger still. Factor in the replacement point: a pair that is past its wash life will leak sooner.

Period underwear and comfort.

Synthetic gussets can feel warm, and some people with sensitive skin react to treatments or dyes. If you notice itching or irritation, wash new pairs before wearing, try a cotton or modal pair, and see a clinician if it persists, since irritation can have other causes. Our vaginal odor and burning after sex pages cover the common ones. None of this is medical advice.