How to Shop for Underwear Online Without Getting the Size Wrong

Quick answer

To buy underwear online without getting the size wrong, measure your hips and waist with a soft tape, compare those numbers to the brand's own size chart rather than your usual clothing size, and check how much stretch the fabric has. Order one or two pairs first when you are trying a new brand, then commit to multipacks once you know your fit.

Buying underwear online should be simple, but sizing is where most orders go wrong. A pair that looks perfect in photos can dig in, ride up, or feel too loose if you rely on the size you wear in jeans or dresses.

The fix is not a secret formula. It is a short, repeatable process: measure yourself properly, read the brand's size chart, understand how the fabric behaves, and test one pair before buying a pack. This guide walks through each step and flags the mistake that trips most people up.

Step 1: Measure your hips and waist, not your clothing size

Your jeans size tells you almost nothing about your underwear size because denim and underwear are cut differently and use different size scales. Grab a soft measuring tape and measure your hips at the fullest point, usually around the widest part of your seat, keeping the tape level and snug but not tight. Then measure your natural waist, the narrowest part above your belly button.

Write both numbers down in centimetres and inches. If you are between sizes, size up for briefs and bikinis where coverage matters, and consider your preferred fit for g-strings. The most common mistake here is measuring over clothing or pulling the tape tight to get a smaller number. That gives you a false reading and a pair that digs in.

• Measure in front of a mirror so you can keep the tape level.
• Measure at the end of the day when your body is at its natural size.

Step 2: Read the brand's size chart, not a generic one

Every brand grades its patterns differently, so a medium in one label can match a large in another. Always open the specific product's size chart on the page you are buying from, and match your hip measurement first, then your waist. Hips usually determine fit more than waist for briefs and bikinis.

If the chart lists a range, say 95 to 100 cm, and you measure 99 cm, you are at the top of that size. That is a checkpoint: check whether the fabric has stretch and whether reviews mention running small. The mistake to avoid is assuming your usual letter size carries over. It often does not.

• Screenshot the size chart before you buy so you can compare if you reorder.
• If you are between sizes and the fabric is firm, choose the larger size.

Step 3: Check the fabric and stretch before you commit

Fabric composition tells you how forgiving the fit will be. Modal blends with a small percentage of elastane stretch and recover, which helps underwear move with you instead of cutting in. A high-waisted brief with a thick waistband will feel firmer than a lightweight g-string, so the same size can behave differently across styles.

For example, the ChiChi Modal Brief Underwear uses a thick, firm waistband that holds you in, while the Cheeky Modal G-String Underwear has a flexible waistband designed to stay put without digging. Neither is better or worse, but they demand different sizing choices. The mistake is ordering the same size across every style in one order without checking each product's fit notes.

• Look for elastane in the blend if you want stretch and shape recovery.
• Firmer waistbands usually mean you should size up if you are between sizes.

Step 4: Order one pair first when trying a new brand

When you buy underwear online from a brand you have not worn before, order a single pair or a small set before committing to a multipack. Wear it for a full day, including sitting, walking, and whatever else your routine involves. That is the only real test of whether the waistband stays put and the leg line sits where you want it.

If the single pair fits well, then move to multipacks, which usually offer better value per pair. The mistake is buying a seven-pack in a new brand based on guesswork. If the size is wrong, you are stuck with several unwearable pairs instead of one.

• Wear the test pair for at least a full day before deciding.
• Check the care label before washing so you do not shrink your test pair.

Step 5: Use multipacks once you know your size

Once you have confirmed your size in a specific style, multipacks become the efficient choice. They reduce the per-pair cost and take the guesswork out of restocking. This is also where colour decisions matter: a mixed nudes set gives you options under light clothing, while an all-black pack is simpler for daily rotation.

The ChiChi Support Modal G-String Underwear - Mixed Nudes comes in White, Bone, Beech and Black, which covers most outfit needs in one purchase. The mistake at this stage is switching styles within the same multipack order without rechecking the size chart, because a high-waisted g-string and a standard brief can fit differently even in the same brand.

• Buy multipacks in the exact style and size you have already tested.
• If a pack mixes styles, check the size chart for each one.

Step 6: Know what to do when the size is still wrong

Even with careful measuring, sometimes the fit is off. Before you order, check the brand's returns or exchange policy for underwear, since hygiene rules often limit returns on worn items. If you cannot return, a pair that is slightly too large is usually more comfortable to live with than one that is too small, because you can adjust the waistband or reserve it for low-movement days.

If the issue is the waistband digging in rather than overall size, the style may be the problem, not the size. A high-waisted brief with a compression waistband is designed to hold firm, while a minimal g-string with a flexible waistband is designed to disappear. The mistake is assuming every discomfort means you ordered the wrong size when a different cut would solve it.

• Check the returns policy before ordering, especially for multipacks.
• If one area digs in but the rest fits, try a different cut in the same size.

Your online underwear sizing checklist

1. Measure hips and waist with a soft tape: Measure hips at the fullest point and waist at the narrowest point, keeping the tape level and snug but not tight. Checkpoint: write both numbers down before you open any product page.
2. Match your numbers to the brand's own size chart: Use the specific product's chart, not a generic conversion, and match hips first for briefs and bikinis. Checkpoint: if you are between sizes, size up for firm waistbands.
3. Check fabric stretch and waistband style: Modal blends with elastane stretch and recover; a thick compression waistband fits firmer than a flexible one. Checkpoint: a firm waistband usually means size up if you are on the edge.
4. Order one pair before a multipack: Test a single pair for a full day in a new brand or style before committing to a pack. Checkpoint: if the single pair fits, multipacks are the better value next step.
5. Recheck the size chart for every style in a mixed pack: A high-waisted g-string and a standard brief can fit differently even in the same brand and size. Checkpoint: do not assume one size fits every cut in your order.
6. Know the returns policy before you buy: Hygiene rules often limit returns on worn underwear, so check the policy for the exact product you are ordering. Checkpoint: if returns are limited, start with one pair and expand once you are sure.

Product facts that help with sizing

• ChiChi Modal Brief Underwear 7 Pack - Black: High-waisted, shape-shifting bikini brief with a thick, firm waistband that holds you in, made from 78% Lenzing Modal, 17.8% Polyamide, 4.2% Elastane. The firm waistband and high waist mean this brief fits more snugly than a standard cut, so if you are between sizes, choose the larger one for all-day comfort.
• Cheeky Modal G-String Underwear: Minimal G-string cut with a semi-seamless finish and a flexible waistband that stays put without digging or slipping, made from Lenzing Modal blended with Polyamide and Elastane. The flexible waistband is more forgiving than a compression band, so you can often wear your usual size without sizing up.
• ChiChi Support Modal G-String Underwear - Mixed Nudes: High-waisted G-string with firm support around the waist and soft, second-skin breathability below, available in White, Bone, Beech and Black. The compression waistband hugs without squashing, so check the size chart carefully if you prefer a looser feel around the waist.

Shopping for underwear online gets much easier once you stop guessing and start measuring. Measure your hips and waist, use the brand's own size chart, check how the fabric and waistband behave, and test one pair before you buy a pack. Do that, and you will avoid the wrong-size cycle for good.