Finding a wireless bra that fits starts with two numbers, not a guess. In this guide, you will learn how to measure your bra size at home in about five minutes, how to read the COCOMARTS Jelly Bra size chart, and how to tell whether a no underwire bra is the right size for you. No fitting room, no guesswork.
What You Need Before You Measure
Before you start, find a soft measuring tape. If you do not have one, you can measure without a tape measure: wrap non-stretch string around your ribcage, mark the overlap, and measure that length against a ruler.
Two habits separate a good measurement from a misleading one. Measure without a bra, or in a thin, unpadded style, because a push-up or padded bra adds volume to your bust measurement and compresses your underbust. And measure at the end of the day, when your measurements are at their most typical. Learning how to measure your bra size takes five minutes, and the payoff is a bra that fits from the first wear.
How to Measure Your Bra Size in Two Steps
Here is how to measure your bra size with nothing but a tape measure.
Step 1: Measure Your Underbust (Your Future Band Size)
Wrap the tape directly under your bust, snug against your ribcage, level and parallel to the floor. Breathe out normally and read the number. It should feel snug, snug enough that you can just slide two fingers underneath, but not dig in. Round to the nearest even number: a 33-inch measurement becomes a 34 band.
Step 2: Measure Your Bust
Wrap the tape around the fullest part of your bust, again parallel to the floor. Keep it relaxed so it skims the surface without compressing breast tissue; pressure here gives an artificially small cup measurement.
Now subtract your underbust from your bust. Each inch of difference equals one cup size: one inch is an A cup, two inches a B, three inches a C. Combine the two results for your starting size. COCOMARTS builds its own chart on top of these two measurements, as the next section shows. For a visual walkthrough, see the COCOMARTS size guide.
How to Read the COCOMARTS Jelly Bra Size Chart
COCOMARTS sells its wireless bras in letter sizes, from S to 3XL on most styles, rather than band-and-cup labels. The brand's bra size chart converts your two measurements into that system.
Step 1: Turn Your Measurements Into a Size
Your cup letter comes from the difference between your bust and underbust measurements, and your band number comes from the underbust measurement itself:
| Your measurement | Gives you |
|---|---|
| 3" - 4" difference | Cup A |
| 4" - 5" difference | Cup B |
| 5" - 6" difference | Cup C |
| 6" - 7" difference | Cup D |
| 7" - 8" difference | Cup DD |
| 28" - 30" underbust | Band 32 |
| 30" - 32" underbust | Band 34 |
| 32" - 34" underbust | Band 36 |
| 34" - 36" underbust | Band 38 |
| 36" - 38" underbust | Band 40 |
| 38" - 40" underbust | Band 42 |
| 40" - 42" underbust | Band 44 |
| 42" - 44" underbust | Band 46 |
Data compiled on October 27, 2026; check official sites for current details.
Step 2: Convert to the COCOMARTS Letter Size
The conversion table maps a traditional US band-and-cup size to the COCOMARTS letter size used on product pages:
| US size | 32 | 34 | 36 | 38 | 40 | 42 | 44 | 46 |
|---|---|---|---|---|---|---|---|---|
| A | S | S | M | L | XL | 2XL | 3XL | 4XL |
| B | S | S | M | XL | 2XL | 3XL | 4XL | / |
| C | S | M | L | XL | 2XL | 3XL | / | / |
| D | M | M | L | 2XL | 3XL | / | / | / |
| DD | M | L | XL | 2XL | / | / | / | / |
Data compiled on October 27, 2026; check official sites for current details.
One practical note: current styles run from S to 3XL, and the Scalloped No Underwire Seamless Push Up Bra extends to 4XL. If your measurements point outside a style's range, that style is not cut for your frame.
Why Wireless Bra Sizing Feels Different
Once you know how to measure your bra size, sizing a wireless bra comes down to how the band and cups behave. An underwire bra gets its structure from the wire; a wireless bra has none, so the band and the support built into the cups carry more of the job. COCOMARTS Jelly Bras use a W-shaped jelly strip inside the cups for support, a feature described on each product page, along with adjustable straps and a multi-row hook closure.
The fabric matters too: COCOMARTS lists its jelly bras as 55% nylon and 45% spandex, a stretchy knit that loosens over time. If a new wireless bra already fits on the loosest hook, consider sizing down.
A quick fit check applies to any wireless bra. Raise your arms overhead: the back of the band should stay level with the front; if it rides up, the band is too large. You should also be able to slide two fingers under the band: if a whole hand fits, it is too loose; if two fingers do not fit, it is too tight.
Common Fit Problems and What They Mean
Most bra fit problems trace back to a handful of causes:
| What you notice | Likely cause | What to try |
|---|---|---|
| Band rides up your back | Band too large | Size down one band, up one cup |
| Cups gap at the top | Cup too large | Size down one cup |
| Tissue spills over the cups | Cup too small | Size up one cup |
| Straps dig into shoulders | Band too loose | Snugger band, not tighter straps |
| Center front does not sit flat | Cup or band mismatch | Recheck both measurements |
| Band feels restrictive | Wrong band size | Looser hook, then recheck |
Tightening the straps is the most common reaction to a loose band, and the least effective: straps that carry a load they were not designed for will dig into your shoulders while the band keeps riding. Fix the band first.
Sister Sizing: What to Do When You Are Between Sizes
Sister sizes are adjacent sizes that share the same cup volume with a different band: a 34C, a 36B, and a 32D all hold roughly the same cup. Knowing how to measure your bra size is the start; sister sizing is the fine-tuning.
- Cups fit, band too loose: go down one band and up one cup, so a 34C becomes a 32D.
- Cups fit, band too tight: go up one band and down one cup, so a 34C becomes a 36B.
- Cups spill but the band feels right: the band is likely riding or shifting; recheck the band before changing the cup.
For more on cup construction, bands, and straps, see the wireless bra guide.
Choosing Your First COCOMARTS Jelly Bra
Now that you know how to measure your bra size, the next question is style. Three starting points cover most everyday needs, all priced at $29.99 as of October 27, 2026.
- The Jelly Bra No Underwire Full Coverage T-Shirt Bra (S to 3XL) is the everyday workhorse: full coverage cups, a wide scoop neckline that stays smooth under T-shirts, and adjustable straps.
- The Jelly Bra Scalloped No Underwire Seamless Push Up Bra (S to 4XL) adds lift and shape with removable pads, a scalloped neckline, and the widest size range in the lineup.
- The Jelly Bra Seamless Full Support Wireless Plunge Everyday Bra (S to 3XL) is built for lower necklines, with a deep V front and semi-fixed pads.
You can also shop all Jelly Bra styles in the Bras collection to compare necklines, colors, and sizes side by side.
One safety net is worth knowing: COCOMARTS offers a 30-day return policy for items that are unworn, unused, and with tags attached. There are no direct exchanges, so if a size does not work, the fastest path is a return for a refund plus a new order. Details are on the refund policy page.
Frequently Asked Questions
How do I measure my bra size at home?
You need a soft tape measure and two numbers: measure snugly under your bust for your band, then around the fullest part of your bust for your cup. The difference gives your cup letter, and the COCOMARTS size chart converts both into its S to 4XL sizing.
Should I measure with or without a bra on?
Without a bra is most accurate. If you prefer to wear one, choose a thin, unpadded style: padded or push-up bras add volume to the bust measurement and compress the underbust.
How often should I measure my bra size?
Every six to twelve months is a sensible baseline. Remeasure sooner after significant weight changes, during or after pregnancy, or when bras that used to fit start riding up.
Do COCOMARTS wireless bras run true to size?
COCOMARTS sizes its wireless bras in S to 4XL letter sizes using the conversion chart above, and the knit fabric has real stretch. Treat your measurements as a starting point, then apply the band level and two-finger checks.
What if I am between sizes?
Try the sister size that keeps the same cup volume with a different band. If your cups fit but the band rides up, size down one band and up one cup. If the band feels tight but the cups fit, do the reverse.
Can I return a bra if the size is wrong?
Yes. COCOMARTS accepts returns within 30 days of delivery for items that are unworn, unused, and with tags attached. Exchanges are not offered, so you would return the item for a refund and order again.
