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38G Bras: What a UK 38G Cup Is, and Why It's a US 38I
A 38G isn't one size — it's one size written in two alphabets. The band is a 38 in every system. The cup is where they split: most full-bust brands label it the UK way, where G sits high on the ladder and equals a US I.
Below: exactly what 38G converts to across US, UK and EU, why a US 38G is actually a smaller cup, how to measure to be sure, your sister sizes, and the styles built to hold a full cup all day.
What is a 38G bra size?
A 38G bra has a 38-inch underband and a G cup — but the cup depends on the sizing system. In UK sizing, which most full-bust brands use, 38G equals a US 38I and an EU 85I, and describes a bust roughly 9 inches larger than the band (around 45 inches around the fullest point). The catch that trips shoppers up: a US 38G is a different, smaller cup — it lines up with a UK 38F. So if you wear a UK 38G, reach for a US 38I, not a US 38G. Sister sizes, holding the same cup volume, are 36GG and 40FF (36J and 40H in US letters). Shop 38G bras in t-shirt, strapless, sports and full-figure styles.
How to choose a bra at 38G
A full cup asks more of a bra than a smaller size does. Five things decide whether it holds all day or gives up by noon.
| What to check | What good looks like | Why it matters |
|---|---|---|
| Band fit | Level all the way around, snug on the loosest hook, two fingers under it and no more | At a full cup the band carries almost all the support — a band that rides up throws the entire load onto your shoulders |
| Cup construction | Three- or four-part seamed cups, or moulded cups with a side support panel and a sling | Seams and slings project a full cup forward and contain it; an unseamed stretch cup collapses at this volume |
| Underwire | Tall, wide wires that encircle the whole breast and sit flat on the ribcage without poking the underarm | A short or narrow wire rides up onto breast tissue — that's a fit fault at this size, not a comfort quirk |
| Straps | Wide, cushioned, set closer to the neck, fully adjustable, ideally with a leotard or U back | Thin straps at a full cup dig grooves into the shoulder; width spreads the load the band leaves behind |
| Gore & wings | Centre gore flat to the breastbone; tall side wings (three or four hooks) | A floating gore means the cup is too small; tall wings stop side spillage and anchor the band |
38G in US, UK, EU and beyond
The same body, seven labels. This is where cross-system shopping goes wrong — the band never changes, the cup letter always does.
| System | Size | How it's written |
|---|---|---|
| UK | 38G | The size on this page — used by most full-bust brands |
| US | 38I | US skips the doubles and runs the alphabet above DDD |
| EU | 85I | Band in centimetres; US 38 = EU 85 |
| France / Spain | 100I | EU band plus 15 — same body, bigger number |
| Italy | 4I | Italy numbers bands; EU 85 = Italian 4 |
| Australia / NZ | 16G | Numeric band (US 38 = AU 16), UK-style cup letter |
| Japan | 85I | EU band; Japanese cups run small, so size up one cup |
So is a UK 38G the same as a US 38G? No — and this is the most common 38G mistake. The letter "G" means about 7 inches of bust-to-band in US sizing and about 9 inches in UK sizing, a two-cup gap. A US 38G is a UK 38F; the UK 38G on this page is a US 38I. If a brand's chart looks a couple of letters off from what you expect, that's the US–UK split, not an error. Treat the conversion as the size to try first, then check the brand's own chart — see our full bra size conversion guide.
Find your 38G bra
Pick the card that matches what you need it for — then tap through to shop.
Everyday, under everything
A moulded t-shirt bra with a side sling: smooth under knit, structured where a full cup needs it.
Shop t-shirt bras →Full coverage all day
Seamed cups, wide straps, tall wings, a firm band. The workhorse category at this size.
Shop full figure →Running, lifting, moving
Encapsulation, not compression. Separate structured cups beat a squash-it-flat crop at 38G.
Shop sports bras →Strapless that stays
At a full cup, strapless lives or dies on the band. Look for longline cuts and silicone grip.
Shop strapless →Smooth the line
A minimizer redistributes rather than flattens — a cleaner profile under a blouse without losing support.
Shop minimizers →Not sure it's your size?
If your current 38G gapes or the gore floats, the conversion or your measurements may be off. Start here.
Convert my size →The band does the lifting; the straps only steady it. Get a full cup fitted to that rule and the grooves, the ride-up and the four-o'clock ache mostly disappear.
The HauteFlair StandardThe complete 38G sizing guide
Measuring, the US–UK gap, sister sizes, the fit tells and the vocabulary.
01How to measure for a 38G at home+
Two measurements, taken in a soft unpadded bra or none at all, tape level:
- Band: snug around the ribcage directly under the bust. A 38 band comes from an underbust near 37–39 inches.
- Bust: around the fullest point, tape parallel to the floor, not pulled tight. At 38G that lands around 45 inches.
- Cup: subtract band from bust. A 9-inch difference is a UK G (US I); 8 inches is a UK FF, 10 a UK GG.
The result is a starting size, not a verdict. Cut varies mill to mill, so let the fit checks below decide — and if you're on the line between letters, try the size plus its sister sizes.
02US 38G vs UK 38G: the two-cup gap+
The label reads differently because the two systems count differently above D:
- UK ladder: D, DD, E, F, FF, G, GG, H — single letters with doubles. UK G sits at about 9 inches.
- US ladder: D, DD, DDD, then G, H, I, J, K — stacked D's, then a straight alphabet with no doubles.
- The result: a UK 38G is a US 38I; a US 38G is a UK 38F. Same word, different cup.
Most full-bust labels (Panache, Freya, Fantasie and the like) are UK-sized, which is the G on this page. If you've been buying US-labelled bras, don't assume the letter carries over.
03Sister sizes: 36GG, 38G, 40FF+
Cup volume moves with the band, so 38G has neighbours holding roughly the same cup:
- Down a band, up a cup: 36GG (36J in US letters) — for a firmer band that feels tighter.
- Up a band, down a cup: 40FF (40H in US letters) — for a looser band with the same cup room.
Reach for a sister size when the cup fits but the band doesn't, or when your exact size is out of stock in a style you want. What you should never do is loosen the band to fix the cup — that hands the support to your shoulders. The full logic is in our sister sizes guide.
04The five fit tells at a full cup+
Stand at a mirror. In order of usefulness:
- Band riding up at the back — band too loose. Go down a band, up a cup (your sister size).
- Gore floating off the breastbone — cup too small, or the wire is too narrow for you.
- Spillage at the top, underarm or under the wire — cup too small. Not a shape problem.
- Wrinkling or gaping at the top of the cup — cup too big, or the wrong style for your shape.
- Straps digging deep grooves — you've tightened them to cover for a loose band. Fix the band first.
Check on the loosest hook when the bra is new; you move to the tighter hooks as the elastic relaxes over time.
0538G, UK G, US I: the vocabulary+
- 38G — a 38 band with a UK G cup, the convention most full-bust brands print.
- US 38I — the same body in US letters, because US sizing runs a straight alphabet above DDD.
- EU 85I — the same body again; 85 is the band in centimetres, not the bust.
- Full bust vs plus size — 38G is a full-bust size (a large cup on a mid band), which is built differently from a plus-size bra (a larger band).
- Sister size — a different band-and-cup pairing holding the same cup volume; 38G's are 36GG and 40FF.
38G bras FAQ
The questions shoppers ask most, answered straight.
What is a 38G bra size?
A 38G has a 38-inch underband and a G cup. In UK sizing — used by most full-bust brands — that's a bust about 9 inches larger than the band (around 45 inches around the fullest point), equal to a US 38I and an EU 85I. It's a full-bust size: a large cup on a mid-size band.
Is 38G a UK or US size?
Almost always UK. Most brands that make a G cup — Panache, Freya, Fantasie and similar full-bust labels — use UK sizing, where the ladder runs D, DD, E, F, FF, G, GG, H. So a 38G you see in stock is generally a UK 38G, which converts to a US 38I.
What is a 38G in US sizing?
A UK 38G is a US 38I. US sizing stacks D's (DD, DDD) and then runs a straight alphabet with no doubles, so the UK's G lands at I. The band stays a 38 in both systems — only the cup letter changes.
Is a 38G the same as a 38I?
Yes, across systems: a UK 38G and a US 38I describe the same cup volume on the same band. If you've been fitted in one system and are shopping a brand that uses the other, this is the pair to remember.
What is a US 38G in UK sizing?
A US 38G is a UK 38F — a smaller cup than the UK 38G on this page. This is the trap in G-cup shopping: the same letter sits at about 7 inches of bust-to-band in the US and about 9 inches in the UK. Always check which system a brand uses.
Is 38G a big bra size?
It's a full-bust size, larger than average, but the letter alone doesn't tell the whole story. Cup volume is measured against the band, so a 38G holds more than a 36G (smaller band) and less than a 40G (larger band) even though all three read "G". The band is half the size.
What are the sister sizes for 38G?
36GG and 40FF — the same cup volume on a different band. Drop to 36GG for a firmer band, move up to 40FF for a looser one. Use a sister size when the cup fits but the band doesn't, or when your size is sold out in the style you want.
How do I measure for a 38G at home?
Measure snugly around your ribcage under the bust for the band, then around the fullest point with the tape level. Subtract the first from the second: a 9-inch difference on a 38 band points to a UK G (US I). Treat it as a starting size and let the fit checks decide.
What bra styles work best for a 38G?
Anything built around a firm band and structured cups — three- or four-part seamed cups, or moulded cups with a side sling. Wide, cushioned straps and tall side wings stop grooves and spillage. Under knits, a t-shirt bra with a sling gives structure without a visible seam.
Do you carry 38G sports bras and strapless?
Yes. For sport at 38G, choose an encapsulation style with separate structured cups rather than a compression crop. For strapless, look for a longline or firmer band with silicone grip. Browse sports bras and strapless.
My 38G doesn't fit — what's wrong?
Usually one of two things: the band is too loose (it rides up and the straps dig), or the size was converted wrong from another system. Re-measure, confirm whether the brand is UK- or US-sized, and try your sister sizes. Our size conversion guide resolves most cross-system mix-ups.
Sizing guidance here is general. Bra sizing is not standardised — cup labelling, wire shape and band firmness vary by brand and style, so conversions are a starting point, not a guarantee. Always check the individual brand's size chart and treat any measurement as a place to begin. Size availability reflects current stock. Last reviewed August 2026.
Shop 38G bras
A UK 38G (US 38I) in t-shirt, strapless, sports and full-figure styles — firm bands, structured cups, and straps that stay where you put them.