If you've heard of period pants, you're likely wondering what all the hype is about. Whether you're completely new to period underwear or simply curious whether it's the right fit for your flow, you're in the right place. Here's your complete guide, from how they work and who they're for, to how to wash them and make them last for years.
Quick Guide: Period Pants Essentials
- Period pants are reusable underwear with a built-in absorbent layer — no pads, no tampons, no inserts required.
- A single pair can absorb the equivalent of 2 to 3 tampons, depending on the style.
- Ruby Cup offers two collections: Flow Freedom (heavy flow, up to 50ml) and Fearless (light to medium flow, everyday wear).
- They are made from OEKO-TEX certified, chemical-free materials — safe for all skin types.
- Both come in sizes XXS to 4XL, making them a genuinely inclusive option — including for plus-size bodies.
- With proper care, one pair lasts up to 5 years, replacing hundreds of disposable products.
- They can be worn alone or combined with a menstrual cup for extra protection.
- Care is simple: cold rinse → cool machine wash → air dry.
Table of Contents
- What Are Period Pants?
- How Do Period Pants Work?
- The Environmental Case for Period Underwear
- Period Pants vs. Pads vs. Tampons
- Are Period Pants Safe?
- Who Can Wear Period Pants?
- How to Choose the Right Pair
- Ruby Cup's Period Pants Collections: Flow Freedom vs. Fearless
- Period Pants for Plus-Size Bodies
- How to Wear and Care for Period Pants
- Can You Use Period Pants with a Menstrual Cup?
What are Period Pants?
Period pants, also called period underwear or period panties, are specially designed underwear with a built-in absorbent layer that replaces (or backs up) pads, tampons, and liners during your period. On the outside, they look and feel just like regular underwear. On the inside, a multi-layer absorbent gusset quietly does all the work: soaking up your flow, locking in moisture, and keeping you fresh and leak-free.
The concept is simple: instead of attaching a product to your underwear, the protection is woven into the underwear itself. No wings, no strings, no applicators — just soft, stretchy fabric and all-day confidence.
Period underwear has gained enormous popularity over the last decade as awareness of sustainable period care has grown. Today, options range from ultra-thin styles for light days to high-capacity pants designed for the heaviest days of your cycle.
How do period pants work?
Period pants use a layered fabric system to absorb and contain menstrual fluid. A typical pair like Ruby Cup's is built with multiple distinct layers, each with a specific job:
-
Top layer (inner): A soft, moisture-wicking fabric sits directly against your skin. It draws fluid away quickly so you feel dry, not damp.
-
Middle layer (absorbent core): A highly absorbent layer — a polyester and nylon blend — traps and locks in fluid, preventing it from returning to the surface.
-
Outer layer (leak-proof): A tightly woven, leak-resistant fabric on the outside prevents any fluid from seeping through to your clothes.
Together, these layers create a product that can absorb the equivalent of two to three tampons or maxi pads in a single pair. Ruby Cup's Flow Freedom pants hold up to 50ml — the same as three super tampons — while Fearless Underwear is designed for lighter days, absorbing the equivalent of two light tampons or liners.
Because the layers are sewn directly into the gusset of the underwear, there's nothing to shift, bunch, or fall out of place. The fit stays secure whether you're sitting at your desk, heading to the gym, or sleeping through the night.
The Environmental Case for Period Underwear
If you've ever thought about the waste generated by a single period, the numbers are sobering. A conventional pack of sanitary pads contains the equivalent of about four plastic bags' worth of plastic components. These are single-use and non-biodegradable: Every pad ever used still exists somewhere on the planet. A single disposable pad can take up to 800 years to fully biodegrade.
Tampons aren't off the hook either. Many contain synthetic fibres, come wrapped in plastic applicators, and contribute significantly to landfill and ocean plastic waste. To achieve the bright white, odourless appearance many people expect, both pads and tampons are often treated with chemicals that can be absorbed through skin during use.
Period underwear flips this equation. One pair of Ruby Cup period pants can replace hundreds of disposables over its lifetime. With proper care, a single pair lasts up to five years, saving you money and dramatically reducing your environmental footprint.
Period Pants vs. Pads vs. Tampons
|
Ruby Cup Period Pants |
Disposable Pads |
Tampons |
|
|
Reusable |
✅ Yes (up to 5 years) |
❌ No |
❌ No |
|
Plastic-free |
✅ Yes |
❌ Contains plastic |
❌ Often has plastic applicator |
|
Chemical-free |
✅ OEKO-TEX certified |
❌ Bleached & treated |
❌ Bleached & treated |
|
Comfort |
✅ Feels like regular underwear |
⚠️ Can shift or bunch |
⚠️ Insertion required |
|
Environmental impact |
Low |
Very high |
High |
|
Long-term cost |
Low |
High (recurring) |
High (recurring) |
|
Absorbency |
Up to 3 super tampons per pair |
Varies |
Varies |
|
Size range |
XXS–4XL |
Limited |
One size |
Over 90% of people start their period journey with single-use products — not because they're better, but because they're the most visible option at the pharmacy. Period underwear, once discovered, tends to become a permanent fixture in the routine.
Are Period Pants Safe?
Yes, when made with high-quality, certified materials, period pants are completely safe. Ruby Cup's period underwear carries the OEKO-TEX Standard 100 certification, one of the most rigorous textile safety standards in the world. Every component, from the inner layer against your skin to the outer shell, is tested for harmful substances, including pesticides, heavy metals, formaldehyde, and pH disruption.
Ruby Cup's period pants are also completely chemical-free, with no bleaching agents, fragrances, or synthetic coatings that could irritate sensitive skin or disrupt your natural vaginal microbiome.
If you have particularly sensitive skin or are prone to yeast or bacterial infections, change your period pants more frequently and ensure you rinse and wash them thoroughly after each wear. Always air dry — a tumble dryer degrades the fabric and reduces effectiveness over time.
Who Can Wear Period Pants?
Period pants are designed for anyone who menstruates, regardless of age, body type, or flow level.
Teens
Period pants are an excellent first period product for teenagers. They eliminate the anxiety of pad shifting or tampon insertion, and can cover an entire school day — including gym class and after-school activities — without needing a bathroom trip to change. Many teens find that period underwear gives them the confidence to carry on with their day without worrying about leaks or stains.
Adults
Whether you're heading to the office, hitting the gym, or running errands, period underwear fits seamlessly into daily life. Many people wear them as their sole period product on lighter days and pair them with a menstrual cup on heavier ones for maximum protection. They're also ideal for overnight use, since they cover more surface area than a pad and won't shift during sleep.
Perimenopause
Irregular or unpredictable periods are common during perimenopause. Period pants provide reliable backup protection on days when your cycle surprises you — or comfortable everyday wear when you know your period is coming but aren't sure exactly when.
How to Choose the Right Pair
There are two key decisions when choosing period pants: absorbency level and size.
Absorbency Level
Match your underwear to your flow:
-
Heavy flow days: Choose a high-absorbency style like Ruby Cup's Flow Freedom, which holds up to 50ml (equivalent to 3 tampons or maxi pads). Ideal for the first two to three days of your cycle, overnight use, or naturally heavy periods.
-
Light to medium flow days: Ruby Cup's Fearless Underwear is designed for the tail end of your period or more manageable flow days. Also perfect as backup when wearing a menstrual cup.
As a general rule: if your flow is heavy, don't underestimate your absorbency needs on day one. It's better to have more protection than you think you need, especially when getting used to period underwear for the first time.
Size
Period pants should fit comfortably without digging in or gaping at the gusset — that's where the leak protection is. Ruby Cup offers sizes from XXS to 4XL. See the next section for more on sizing, especially for plus-size bodies.
Period Pants for Plus-Size Bodies
Finding period protection that actually fits, and stays in place, can be frustrating, particularly for people with fuller hips, thighs, or a higher waist. Standard sizing in period care has historically been an afterthought, and that's something Ruby Cup has made a deliberate effort to address.
Ruby Cup plus-size period pants are available in sizes up to 4XL, with an inclusive size range running from XXS to 4XL across both the Flow Freedom and Fearless collections. The key to a great fit in period underwear isn't just the waistband — it's the gusset. A pair that fits well around the hips but gapes at the inner thigh won't provide the leak protection it promises. Ruby Cup's size guide is based on hip measurements rather than arbitrary sizing conventions, so you can find a pair that sits flush, stays comfortable, and actually does its job.
For plus-size wearers, a few additional tips:
- Prioritise hip measurement over waist. Period pants live at the hips and thighs, so that measurement is the most important one to get right.
- Flow Freedom works well for plus-size wearers on heavier days, as the hipster cut and wider gusset provide more complete coverage.
- Fearless is the go-to for lighter days and as everyday backup — its stretchier, lower-cut profile adapts well to different body shapes.
- Try a bundle if you're starting out: It lets you get both styles and figure out which fits your body and your cycle best.
Period pants should feel like regular underwear. If a pair is digging in, riding up, or leaving gaps, it's almost always a fit issue, not a product failure — and trying a size up often solves it entirely.
Ruby Cup's Period Pants Collections: Flow Freedom vs. Fearless
Ruby Cup has developed two distinct collections to match different needs across your cycle. Rather than choosing one over the other, most people find they want both — and the bundle deals make that easy.
Flow Freedom — For Heavy Flow Days
Flow Freedom pants are built for the days when protection matters most. With a 50ml capacity and generous front-to-back coverage, they're designed to keep you confident whether you're at the gym, in a work meeting, or sleeping through the night. The reinforced absorbent gusset handles heavy flow without feeling bulky, and the hipster-style fit works under most outfits.
Best for: Heavy flow days, overnight protection, post-partum light bleeding, active lifestyles.
Fearless — For Lighter Days
Fearless Period Underwear is the everyday hero of the collection. Cut low, thin as regular underwear, and designed to be barely noticeable, it comes in a playful leopard print and absorbs the equivalent of two light tampons or liners. It's the ideal pairing for the end of your cycle or as a backup layer when using a menstrual cup.
Best for: Light days, end of cycle, backup protection with a menstrual cup or disc, everyday confidence.
Good to know: For every pair of Flow Freedom or Fearless pants sold, Ruby Cup donates 2% of revenue to a Learning Centre nursery in Kisumu, Kenya, so your purchase directly supports education.
Flow Freedom vs. Fearless: Side-by-Side
|
Flow Freedom |
Fearless |
|
|
Absorbency |
50ml / ~3 tampons |
~2 light tampons |
|
Best for |
Heavy days, overnight |
Light days, backup use |
|
Feel |
Supportive, full coverage |
Ultra-thin, barely-there |
|
Style |
Hipster |
Low-cut hipster |
|
Certification |
OEKO-TEX Standard 100 |
OEKO-TEX Standard 100 |
|
Lifespan |
Up to 5 years |
Up to 5 years |
Both collections are OEKO-TEX Standard 100 certified and free from harmful substances.
Bundle options are available so you can mix and match across both lines.
How to Wear and Care for Period Pants
Getting started is straightforward, and caring for them properly ensures they last for years.
Wearing Your Period Pants
- Put them on like regular underwear — there's nothing to insert or attach.
- Wear them for up to 8–12 hours, depending on your flow. If you have a heavier flow, check in around the 6-hour mark and change sooner if needed.
- If you're out with a heavier flow, bring a spare pair and a small sealed bag to carry the used pair home.
Washing and Care Step-by-Step
Step 1 — Rinse in cold water: As soon as you take them off, rinse the gusset under cold running water until the water runs clear. Never use hot water at this stage — heat sets stains and damages the absorbent layers.
Step 2 — Machine wash on a cool/cold cycle: Wash with a gentle detergent on a cold or cool cycle (30°C or below). They can go in with the rest of your laundry.
Step 3 — Air dry only: Lay flat or hang to dry naturally. Never put period underwear in a tumble dryer — heat degrades the absorbent layers and shortens the lifespan of the pants significantly.
Step 4 — Repeat: Once fully dry, they're ready to use again. With this routine, Ruby Cup period pants last up to five years.
Pro tip: Keep three to five pairs in rotation, so you always have a fresh pair ready while others are drying.
Can You Use Period Pants with a Menstrual Cup?
Absolutely, and it's one of the most popular combinations. Wearing a menstrual cup alongside period underwear gives you double protection: the cup collects most of your flow internally, while the pants act as a reliable backup in case of any overflow or leaks.
This pairing is especially popular for:
- Heavy flow days when you want maximum confidence
- Overnight use
- Active situations like exercising or long travel
- People who are still learning to use a menstrual cup and want peace of mind while they adjust
Ruby Cup Dynamic Duo, which includes one Ruby Cup menstrual cup and a Flow Freedom period pant
Which pants work best with a cup?
- Fearless Underwear is the everyday pairing — thin, barely-there, and ideal for lighter days when you just want that extra layer of security under your cup.
- Flow Freedom is the go-to for heavier days, overnight, or anytime you want both internal and external protection working together.
For any questions or concerns about your period health, always consult a doctor. For questions about Ruby Cup products, reach out at hello@rubycup.com.
