Everyone's got a list of the best period underwear in Australia. Almost none of them tell you how to choose. So here's the version that's actually useful: match the pair to the day, not to the review score. Most leaks aren't a product failure, they're a light pair doing a day-two job. Work out your heaviest day, buy for that first, then fill in around it. You'll spend less and you'll stop side-eyeing your chair when you stand up.
The short version: the best period underwear for you is the pair that matches your heaviest day, in a cut you'd wear anyway. Start with one heavy pair, one moderate pair and one light pair, then build from there. Absorbency, not brand, is what stops leaks.
What actually makes the best period underwear?
Three things, in this order: how much it holds, how it sits, and whether you'd wear it on a Tuesday with no period in sight.
Everything else is marketing. Lace trim doesn't stop a leak. A five-star review from someone with a light flow tells you nothing about your day two.
Start with absorbency, because that's the only one that fails loudly. Then cut, because a pair that rolls down at the waist will live in the drawer forever. Then looks, because you're allowed to like your underwear.
How do I know which absorbency I need?
Think in tampons, not millilitres. Nobody knows what 30ml looks like. Everyone knows what four tampons feels like.
Scarlet's range, in tampon-equivalents:
- Period G-String, around two tampons' worth. Light days, spotting, discharge.
- Period Bikini Brief, light (around two) or moderate (around three).
- High-Waist Period Brief, around three. The day-two workhorse.
- Period Boyshort, around four. Heaviest day, and built to outlast a full night's sleep.
- High-Waist Pocket Period Brief, light-moderate or moderate-heavy, with a pocket that holds rae.
If you're between two options, size up the absorbency. Nobody has ever regretted being over-prepared at 3am.
New to how the lining works? Start here.
Do period undies actually leak?
They can, and it's almost always one of three things: wrong absorbency for the day, wrong size, or fabric softener wrecking the lining.
Sizing is the quiet one. Too big and the gusset doesn't sit flush, so blood takes the scenic route. Too small and the waistband becomes a countdown timer.
And skip the fabric softener. It coats the fibres and the lining stops doing its job, which is a very expensive way to make your undies worse.
How many pairs do I actually need?
For a full period with no top-ups: five to seven pairs, weighted toward your heavy days.
For a first go, three is plenty. One heavy, one moderate, one light. Wear, rinse, wash, repeat, and see how you actually bleed before you commit to a drawer full. The Underwear Starter Set exists for exactly this reason.
If you're on a heavy flow, or you've got endo or adeno in the mix, plan for more and expect to change during the day. That's not a product failing, that's just the flow.
What about PFAS and "non-toxic" claims?
Ask for lab testing, not adjectives. "Non-toxic" isn't a regulated term, so on its own it means nothing.
Scarlet's undies are PFAS-free and independently lab tested. If a brand can't tell you who tested it and what they tested for, treat the claim as decoration. More on what to check before you buy.
Are period undies cheaper than pads and tampons?
Over a few years, generally yes. In week one, obviously not, because you're buying three years of period products at once.
That's the real barrier and it's fair. Start with one pair for your worst day, the one where disposables let you down most. If that pair earns its place, buy the rest.
Which pair should you start with?
Heavy sleeper, heavy flow: Boyshort.
Day two at work, wants everything to sit flat under trousers: High-Waist Brief.
Light days, spotting, or a back-up under a cup or tampon: Bikini Brief or G-String.
Cramps that need heat during the day: High-Waist Pocket Brief, worn with rae. rae runs 5+ hours on low, around 3 on medium, around 2 on high, so a work day is doable if you're not sitting on high the whole time.
Still deciding? The whole period underwear range is here.
Buy for your worst day. The rest of the month sorts itself out.
Quick answers
How many period undies do I need for one period?
Five to seven pairs covers a full period without washing mid-cycle. Three is enough to start.
How much do Scarlet period undies hold?
Around two tampons' worth for the G-String and light Bikini, around three for the High-Waist Brief and moderate Bikini, and around four for the Boyshort.
Do period undies leak overnight?
Not if the absorbency matches your flow and the fit is right. The Boyshort holds around four tampons' worth and is built to outlast a full night's sleep.
Are Scarlet period undies PFAS-free?
Yes. They're PFAS-free and independently lab tested.
How do I wash period underwear?
Rinse in cold water, then machine wash cold in a mesh bag. No fabric softener, no dryer.
Can I wear period underwear with a cup or tampon?
Yes, plenty of people do on heavy days and use the undies as back-up.