How to Build a Bra and Underwear Starter Kit That Works
By Underdays | Breathable and comfortable everyday TENCEL | Published: 2026-10-13
Category: Buying Guides
A practical underwear starter kit guide: how many pieces you need, which styles to pick first, and how to build a comfortable everyday set without overbuying.
Quick answer
Build your starter kit around one week of wear, not one perfect set. Start with 5-7 briefs or a mix of briefs and thongs, add one or two bras that match your daily routine, and choose adjustable fits so the kit works across your cycle and activity level. A pre-built kit like The Brief Starter Kit or The Black Replenish Kit - Barely There can shortcut the trial-and-error if you already know your size.
Start with your actual week, not a fantasy drawer
Count how many days you need underwear before laundry day, then add one backup. That number is your baseline. If you work out three times a week, add two more quick-dry pieces so you are not hand-washing midweek. The goal is a kit that covers real life, not a capsule wardrobe photo.
- 5-7 everyday briefs for a standard week
- 2-3 extra if you sweat daily or travel often
- 1-2 bras that match your most common outfit necklines
Choose styles by coverage and visibility, not by trend
Briefs give full coverage and stay put under jeans and trousers. Thongs minimize visible panty lines under leggings and fitted dresses. A cheeky cut sits between the two. If you are unsure, start with mostly briefs and one or two thongs so you can test which you reach for. Adjustable fits and extra stretch matter more than the label on the cut.
Fit guidance: how each piece should feel
The waistband should sit flat without digging or rolling. The leg opening should not cut into your hip crease when you sit, squat, or walk. For bras, the underband carries most of the support, so it should feel snug but not restrictive, and the cup should lie smooth without gaping or spilling. If you are between sizes, size up in briefs and adjust the underband on the bra rather than forcing a cup that does not fit.
- Waistband: flat, no roll, no red marks after an hour
- Leg opening: stays put when you move, no digging
- Bra underband: snug enough to stay level in back
- Cup: smooth, no overflow or empty space at the top
Build in stages so you do not overbuy
Buy a small core first, wear it through a full laundry cycle, then fill the gaps you actually noticed. If you keep reaching for the same two pieces, that is your signal to buy more of that style, not to add a new cut. Kits that bundle several pieces at a lower price per item are useful here because they let you test a full week without committing to a single style.
Decision rules for your first kit
- If you are buying underwear for the first time: Start with a small kit that includes a single style in multiple pairs, so you can judge fit before adding variety. Choose The Brief Starter Kit if you want the lowest-risk entry point.
- If you already know you prefer a mix of coverage: Pick a kit that gives you both fuller coverage and a minimal-VPL option in one order. Choose The Black Replenish Kit - Barely There if you want a five-day mix of cheeky and thong.
- If your bra needs to work across workouts and daily wear: Look for a built-in bra with quick-dry fabric so you are not switching bras between errands and exercise. Choose The Everyday Soft Plunge if you want one bra for movement and lounging.
Starter kits and pieces worth knowing
- The Brief Starter Kit: The Brief Starter Kit includes 3 briefs and a pouch, and is described as a first-timer's exclusive to experience Underdays. A low-commitment way to test the fit and fabric before building a full week.
- The Black Replenish Kit - Barely There: The Black Replenish Kit - Barely There combines three Black Cheeky and two Black Thongs plus the Pouch, with adjustable fit and extra stretch. Covers a five-day week with two coverage levels, so you can decide whether you prefer briefs or thongs in daily wear.
- The Everyday Soft Plunge: The Everyday Soft Plunge is described as part activewear, part everyday wear, with a built-in bra and quick-dry workout fabric. Useful as the one bra that works for errands, Pilates, or lounging without changing for each activity.
Who this approach fits
Best for
- First-time buyers who want a complete week of underwear without guessing
- People who want adjustable fit and extra stretch across different days
- Anyone building a small, functional drawer rather than a large collection
Not for
- Shoppers who already have a full drawer and only need one replacement piece
- Anyone looking for a single style in a very large pack without variety
