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How to Choose Period Underwear: Absorbency, Gusset and Fit
Choosing period underwear really comes down to two things: absorbency and where the absorbent layer sits. Capacity has to match your flow, and how far back the layer reaches decides whether a pair suits daytime or sleeping. Every other detail — colour, cut, price — is built on top of those two.
How the leak protection works
A Kiri pair looks like ordinary underwear; the difference is in the gusset, where four layers are bonded together. The wicking layer pulls fluid away so the surface stays dry. An antibacterial layer neutralises the bacteria behind odour. The absorbent core locks liquid in. A leak-proof outer layer stops it reaching your clothes. None of the fabrics contain dioxins, chlorine or rayon.
Read the millilitres, not the adjectives
Ignore "light" and "heavy" and look at the actual number:
- Daywear holds up to 50 ml — roughly 5.5 regular tampons. Enough to wear alone on light to moderate days, or as backup with a tampon or cup on heavier ones.
- Nightwear holds up to 75 ml — roughly 8.5 tampons. The waist sits higher and the absorbent layer runs from front to back, because flow moves backwards when you lie down, so side sleeping is covered.
If your flow varies a lot across a cycle, a day-and-night bundle covers both without deciding up front.
Sizing: what to do if you're between two
Sizes run XS to L, with XL in nightwear. Nightwear is cut slightly closer than daywear, so your size can differ between the two. If you're between sizes, size down — the gusset has to sit flush to work, and a loose waistband lets it shift. Full waist and hip measurements are in the size guide.
Washing, and why it decides the lifespan
Rinse cold until the water runs clear, machine wash cold in a laundry bag, hang to dry. No bleach, no fabric softener, no dryer — heat and softener are what age the absorbent layer. Cared for this way a pair lasts years, replacing hundreds of disposables.
Where to start
Most people only need one pair to understand what pads and tampons were missing. Try a daywear pair on a lighter day at the end of your next period. Browse all period underwear, or the full range.
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