Start beneath the bust
Wrap a soft tape snugly around your ribcage, directly below the breast tissue. Keep it level, breathe normally, and repeat once.
Capire la taglia del reggiseno coppa G
The calculator and detailed guides below are currently in English. Size systems are selected independently of language.
MEASURE WITH CONFIDENCE
G Cup Bra Size Calculator
YOUR PERSONAL FIT STARTS HERE
Find your starting size
Start with two measurements. Choose your label system, explore international equivalents and see exactly how the result is calculated.
Watch the tape follow your measurements.
Select a field to highlight that part of the guide. The displayed lengths update as you type; the drawing changes proportion schematically.
- Use the underbust marker to place the lower tape.
- Move to the fullest bust without pulling tight.
- Compare the two lengths, then check your starting sizes below.
YOUR FIT NOTES
Front view: locate the fullest bust and the ribcage directly below the tissue. Tape loops describe the complete circumference.
Underbust circumferenceEnter a value
Full-bust circumferenceEnter a value
Place the tape directly below the breast tissue. Keep it level and snug without pain.
An illustrated measuring guide, not a scan of your body. Live lengths are circumferences, not screen widths. The three views explain tape placement; their proportions are schematic.
Your measurements, explained.
Enter both values to see your UK and US starting sizes. The result is not restricted to G cup.
Our method & calculation limits ↗
Understand your complete bra size, compare UK and US labels, and check the fit with practical guidance. G is a cup label within a sizing system—not one fixed measurement or body shape.
No account. No measurement uploads.Chart-based conversionsA starting size, with next steps
A TOOL FOR EVERY NEXT QUESTION
Find clarity beyond the cup letter.
Already know your size? Convert the label, compare another band, or work through a fit problem. Each tool explains what the result means.
Size converter
Translate complete labels across a named international chart.
Use the size converter tool ↗Sister sizes
Adjust your band while keeping cup capacity close.
Use the sister sizes tool ↗Fit checker
Work through gaping, spillage, wires and band comfort.
Use the fit checker tool ↗Measurement chart
Explore band-specific examples in inches and centimetres.
Use the measurement chart tool ↗Compare sizes
See how two complete band-and-cup sizes relate.
Use the compare sizes tool ↗Shape & style finder
Turn fit observations into construction features to try.
Use the shape & style finder tool ↗THE TWO Gs ARE DIFFERENT
G ≠ G| Starting label | Chart equivalent |
|---|---|
| 34G UK | 34I US |
| 34G US | 34F UK |
US/UK alignment: Wacoal’s Elomi, Freya and Fantasie chart. Always confirm the product’s label system.
UNDERSTAND YOUR SIZE
What does a G cup
actually mean?
A cup letter describes a position in a sizing system. It does not describe a fixed breast volume, a certain appearance, or one bust measurement for everyone.
The band matters just as much: 30G and 40G are different complete sizes. The system matters too: UK G and US G sit at different points on their cup ladders.
Keep the full label with you—such as 34G UK—when comparing charts or shopping. It is the quickest way to avoid an easy sizing mix-up.
Read the G cup size guide →Schematic comparison, not a body-shape prediction. Read the method.
HOW G CUP BRA GUIDE WORKS
Measure. Understand. Try the fit.
Measure the fullest point
Let the tape rest around your fullest bust without compressing tissue. Use the same unit and check the tape across your back.
Use the result as a starting point
We round the underbust to an even inch band, then map bust minus band to UK and US cups. Confirm the result in a real bra.
Our independent two-measurement estimator does not reproduce the six-measurement A Bra That Fits method. See the complete method and limits.
Schematic comparison, not a body-shape prediction. Read the method.
YOUR COMPLETE SIZE, EXPLAINED
G cup measurements at a glance.
These are worked examples from our simplified band-difference model. They show why a G cup does not have one fixed circumference.
| Band label | UK G bust reference | US G bust reference | UK G sister sizes |
|---|---|---|---|
| 30G guide ↗ | 39 in / 99.06 cm | 37 in / 93.98 cm | 28GG · 32FF |
| 32G guide ↗ | 41 in / 104.14 cm | 39 in / 99.06 cm | 30GG · 34FF |
| 34G guide ↗ | 43 in / 109.22 cm | 41 in / 104.14 cm | 32GG · 36FF |
| 36G guide ↗ | 45 in / 114.30 cm | 43 in / 109.22 cm | 34GG · 38FF |
| 38G guide ↗ | 47 in / 119.38 cm | 45 in / 114.30 cm | 36GG · 40FF |
| 40G guide ↗ | 49 in / 124.46 cm | 47 in / 119.38 cm | 38GG · 42FF |
A reference value is not a guaranteed manufacturer range. Cup shape and brand grading can change your best fit.
Schematic comparison, not a body-shape prediction. Read the method.
YOUR BRA, YOUR EVERYDAY
Find a style that fits your life.
Sports ↗
Movement & secure supportWireless ↗
Softer structure, thoughtful fitStrapless ↗
A stable fit beneath your outfitSwimwear ↗
Cup-sized confidence in the waterConstruction guides, not unverified product rankings. Check the actual size selector and current returns policy before ordering.
Schematic comparison, not a body-shape prediction. Read the method.
WHEN THE NUMBER IS ONLY THE BEGINNING
A right-looking size
can still feel wrong.
Gaping, spillage and pressure do not always point to the same cause. A cup may be too shallow at its base while leaving room at the top. Tight straps can hide a loose band. A wireless centre behaves differently from a wired one.
Our fit checker starts with what you can observe, then gives you the next thing to compare.
Work through my fit →A USEFUL TRY-ON ORDER
01 A comfortable, level band
Check tension independently of the cups when possible.
02 Cups that contain your tissue
Assess pressure and empty space together.
03 Wires and straps that work with you
Support should not depend on painfully tightened straps.
Schematic comparison, not a body-shape prediction. Read the method.
AFTER YOUR STARTING SIZE
Choose your next fitting decision.
A useful size decision connects four things: your measurements, the label system, the garment’s construction and what happens when you wear it. Start with the question you can answer now, then move to the next one.
1. Decide whether you need conversion, sister sizing or a larger cup
Conversion keeps the chart-aligned garment label while translating systems: UK 34G becomes US 34I on this chart. Sister sizing changes the band and moves one cup step in the opposite direction: UK 34G can be compared with 32GG or 36FF. Increasing a cup on the same band is a third operation and changes nominal capacity.
If the band fits but the cup overflows, start by comparing capacity or a more suitable cup edge on that band. If the cups contain comfortably but the band alone is loose, an adjacent sister-size comparison is more relevant. If the garment fits and you are shopping on another regional storefront, establish the displayed system before converting. These tools answer different questions; none should be used as an automatic response to every fit problem.
Schematic comparison, not a body-shape prediction. Read the method.
2. Match the construction to the problem you observe
A gap at the upper edge does not describe the whole cup. If the base also feels compressed, compare depth and height before repeatedly choosing a smaller letter. A low neckline, moulded cup, stretch panel or different wire can change where room and support are provided. Record the location of the issue, not simply “too big” or “too small.”
Then consider the job of the garment. The sports bra planner asks about movement and the problem during that movement. The strapless planner separates slipping from an edge mismatch. The wireless planner focuses on lower-band behaviour and preferred construction without applying a rigid wired-centre rule.
For garments connected to the torso, a cup-only answer can miss the cause. A bodysuit torso comparison or one-piece length check helps investigate vertical pulling. The result remains a comparison with a specific chart, not a prediction of fabric stretch.
Schematic comparison, not a body-shape prediction. Read the method.
3. Make the next purchase an informative comparison
Save the complete size, system, product model and one or two fit observations. For example: “34G UK; band stays level; upper edge gaps; pressure near the wire.” A later try-on is easier to interpret when you know what changed. Comparing several unrelated bands, cups and constructions at once may leave you unsure which difference helped.
Check the actual model-and-colour size selector, not just a collection’s largest cup letter. Read returns, delivery and chart information on the current retailer page. Our order-cost tool adds the prices and fees you enter and makes the cost of a possible return visible. It does not retrieve stock or invent a cheapest seller.
Keep the final decision grounded in comfort and the intended activity. A mathematically aligned label, an attractive drawing or a search result cannot establish how a particular garment will feel on you. The tools below make each next check more specific while keeping those limits visible.
Schematic comparison, not a body-shape prediction. Read the method.
G CUP · THE COMPLETE SIZE GUIDE
G cup bra size: the letter, the band and the system
A G cup is a position in a bra-size sequence, not a single breast measurement. To make it useful, pair it with a band number and a sizing system: 34G UK and 34G US do not describe the same chart position.
Schematic comparison, not a body-shape prediction. Read the method.
UK G versus US G
The UK sequence used here runs D, DD, E, F, FF, G, GG. The US sequence runs D, DD, DDD, G, H, I, J. At the same band, UK G aligns with US I, and US G aligns with UK F on the named conversion chart. There are two aligned cup steps between UK G and US G; the shared letter hides that difference.
Read the product selector before ordering. A US storefront can sell a UK-labelled bra, and another storefront can already display converted sizes. Converting a label twice can undo an otherwise correct choice. If the chart and selector disagree, ask which label will arrive on the garment.
How big is a G cup?
The answer depends on what you want to compare. Within the same system, 38G has more nominal cup capacity than 30G. Across systems, compare equivalent labels first. For appearance, neither comparison is enough: torso shape, tissue distribution and cup construction affect the visible silhouette.
There is no universal “G cup body,” fruit equivalent, breast weight or volume in millilitres. Our shaded mannequin explains where the tape goes. Its proportions cannot predict how your own bust looks, and it is not evidence that one shape is more correct than another.
G cup measurements in inches and centimetres
In this site's independent estimator, UK G corresponds to a rounded nine-inch difference between full bust and the nominal band; US G corresponds to seven inches. Those differences convert to 22.86 cm and 17.78 cm. They are model references, not universal manufacturer measurement intervals. The calculation subtracts the rounded band, which may differ from your raw underbust.
For example, 34 inches underbust and 43 inches bust produce UK 34G / US 34I. The same physical readings are 86.36 cm and 109.22 cm. Changing the input unit must preserve the label. Changing to an EU garment label is a different operation: the sourced chart aligns UK 34G with EU 75I. It does not label an 86.36 cm circumference “EU 86.”
What if the result changes when you measure again?
First check the path of the tape in the side and back views. A diagonal tape or compressed bust changes the input. Then inspect the rounding: an underbust just below 33 inches rounds to a 32 band in this model; exactly 33 rounds to 34. That jump is a calculation boundary, not a sudden change in your body.
Use the optional repeat fields to see whether both readings lead to the same label. If they do not, keep both readings and compare the likely bands for comfort. Do not repeatedly tighten the tape until it returns the size you expected. For a fuller measurement approach, the A Bra That Fits calculator asks for six measurements and uses its own method.
Turn a G cup estimate into a useful fitting decision
Try one construction in the complete suggested size, settle the tissue into the cups and move normally. Note whether the band stays level, where the cup contains or leaves space, and whether the wire follows the breast crease. If the band fits independently but the bra feels tight with the cups in place, investigate cup room before automatically increasing the band.
A cup that gaps above while pressing below can be the wrong shape. A wireless centre can sit away from the sternum without failing the same test as a wired gore. These are separate observations, which is why the fit checker and shape finder ask about a garment you have actually tried.
Keep three notes together: your full label and system, the exact bra model, and what happened during movement. They make a later comparison more useful than “G was too big.” For a stable cup with an unsuitable band, explore adjacent sister sizes; for a different country label, use international conversion.
EVERY QUESTION HAS A NEXT STEP
Explore every G cup calculator and guide tool.
Choose the question you want to answer. Each destination has its own inputs and a result that fits the task: a size calculation, a label comparison, a length or cost calculation, or a construction decision.
33 supporting topic tools and guides, plus the homepage calculator
Measure & check2 tools & guides
Take repeatable measurements and interpret a chart.
Repeat-measurement consistency calculator
First underbust reading · Repeated underbust reading · Full bust
Enter inputs & explore →G Cup Measurements in CM and Inches
Under this site’s simplified band-difference method, UK G uses a 9-inch (22.86 cm) difference and US G uses 7 inches (17.78 cm). These are model references, not universal brand ranges.
Enter inputs & explore →Convert labels2 tools & guides
Translate an existing complete size without mixing systems.
G Cup Bra Size Converter: US, UK and EU
In the Freya chart, 34G UK maps to 34I US, 75I EU, 90I France, 12G Australia and 75J Japan. This is a chart-specific label mapping.
Enter inputs & explore →Japanese G Cup to US and UK: Size Converter
Wacoal Japan places G at approximately a 25 cm bust–underbust difference. Freya’s international label chart uses its own Japanese label alignment. These are different chart contexts.
Enter inputs & explore →Compare sizes2 tools & guides
Understand adjacent band choices and specific cup pairs.
G Cup Sister Size Calculator and Chart
For UK 34G, adjacent sister sizes are 32GG and 36FF. For US 34G, they are 32H and 36DDD. Moving the band and cup in opposite directions is the key.
Enter inputs & explore →G Cup Comparison Tool: Band and Cup Sizes
Keep both systems visible. A 34G UK and 34I US align on the same chart
Enter inputs & explore →Appearance & evidence2 tools & guides
Understand what a label can and cannot reveal about a body.
Solve a fit problem3 tools & guides
Interpret gaping, pressure, unexpected estimates and shape.
G Cup Bra Fit Checker: Gaping, Spillage and Band Fit
Start with band stability, then check cup containment, wire position and straps. Gaping alone does not prove a cup is too large.
Enter inputs & explore →Unexpected-size comparison calculator
Measured underbust · Measured bust · Current bra band · Current UK cup
Enter inputs & explore →Cup depth, edge and wire-width matcher
Near the cup base · Upper cup edge · Wire at the sides
Enter inputs & explore →Choose a bra style15 tools & guides
Choose construction for everyday use, movement or an outfit.
G Cup Bra Guide: Compare Styles, Sizes and Features
Choose your activity and describe the fit problem you want to solve. The tool suggests construction features and checks, without pretending to know live stock.
Enter inputs & explore →Sports bra support planner
Intended movement · What happens when you move?
Enter inputs & explore →Wireless bra structure finder
Preferred feel · What does the lower band do?
Enter inputs & explore →Strapless stability planner
During a reach test · Outfit requirement
Enter inputs & explore →G cup bralette fit planner
Product sizing format · Main use
Enter inputs & explore →Plunge neckline checker
Inner cup edge · Neckline priority
Enter inputs & explore →T-shirt bra edge planner
Under a thin top · At the base of the cup
Enter inputs & explore →Minimizer shirt-fit planner
Main shirt issue · After trying it on
Enter inputs & explore →Push-up padding fit planner
Padding design · Cup-edge result
Enter inputs & explore →Longline torso-clearance calculator
Comfortable space below the wire when seated · Garment extension below the wire
Enter inputs & explore →Nursing bra access planner
Clip or opening test · Current adjustment need
Enter inputs & explore →Low-back outfit clearance calculator
Outfit back edge height above waist · Top of bra back band above waist
Enter inputs & explore →Adhesive outfit decision checker
What do you need? · Before application
Enter inputs & explore →Bustier chart-gap calculator
Your bust · Garment chart bust reference · Your waist · Garment chart waist reference
Enter inputs & explore →Bodysuit torso-length comparator
Your torso measurement · Garment chart torso reference · Measurement method
Enter inputs & explore →Choose swimwear4 tools & guides
Check swim support, hidden layers and torso length.
G cup swimwear construction planner
Water activity · Preferred garment
Enter inputs & explore →Bikini closure planner
Back closure · Activity
Enter inputs & explore →Tankini layer-fit checker
Internal support band · Outer layer
Enter inputs & explore →One-piece swimwear torso checker
Your torso-loop measurement · Garment chart torso-loop reference · Where do you notice pulling?
Enter inputs & explore →Shop & maintain3 tools & guides
Understand retailer labels, ordering costs and wire replacement.
Bra order and return-cost calculator
Item price · Outbound shipping · Known taxes / import fees · Return postage or fee
Enter inputs & explore →Brand-chart question builder
Chart you are reading · Information still missing
Enter inputs & explore →Underwire channel-clearance calculator
Usable channel length · Replacement wire length · Total clearance specified by maker
Enter inputs & explore →QUESTIONS WE HEAR OFTEN
A little more
understanding.
Clear answers to common G cup sizing questions, with US and UK differences kept visible.
Browse tools and specialist guides →G cup bra questions
Is a UK G cup the same as a US G cup?
No. In the named chart used here, UK G aligns with US I, while US G aligns with UK F. Always retain the band too: UK 34G converts to US 34I, not US 36I. Check whether the shop already displays converted labels before converting again.
Can this calculator give EU, French, Australian and Japanese sizes?
Yes, as label equivalents of the UK starting estimate within the Freya chart’s published range: UK bands 28–44 and cups B–K. The Japanese result is explicitly an export-chart label. It is not a Japanese domestic measurement formula, and unsupported sizes display an out-of-chart message rather than an invented conversion.
Should I measure in a padded bra?
Padding can add to the circumference being measured. Follow the measurement method consistently and avoid compressing the fullest bust with the tape. If your readings vary, check tape level, posture and tension before relying on the estimate. A fitting using an actual garment can resolve questions that two measurements cannot.
Why do the front, side and back views show different details?
The front view identifies the two tape positions and displays live circumference labels. The side view shows the fullest point and the underbust below tissue. The back view checks that the tape stays level. The mannequin is a schematic measuring aid; it does not predict a body shape from your inputs.
Are my measurements saved or sent to a server?
The calculator processes measurements in your browser. It does not upload or persist them. Copy my fit notes writes the displayed result to your clipboard only when you request it; clearing the form removes the current values from the tool.
What size is a G cup bra?
G is a cup label within a sizing system. The complete band-and-cup size matters: 32G and 38G have different nominal cup capacities. UK G aligns with US I on the chart used here, while US G aligns with UK F.
What is a G cup in centimetres?
There is no one G cup bust circumference. Our simplified estimate uses a 22.86 cm difference from the nominal band for UK G and 17.78 cm for US G. These are calculation references, not universal body-measurement ranges.
Why does the calculator say G when I wear DD?
Check the units and label system first. A change to a smaller band can also require a larger cup letter. Repeat your measurements and try the suggested size before assuming that either the old or new label must be correct.
What is the sister size of a G cup?
It depends on the band and system. UK 34G has adjacent sister sizes 32GG and 36FF. US 34G has 32H and 36DDD. Sister sizes have similar nominal cup capacity, but their frame and fit can change.
Is gaping always a sign that my cup is too big?
No. A cup can be too tall, too shallow or too closed at one edge and still gape elsewhere. Check where pressure and empty space appear together, then compare cup shape as well as size.
Can I find wireless and strapless bras in G cup?
Look for your complete size in the actual product selector. Both constructions exist in fuller-bust ranges, but coverage and stock vary. Use the style guides to compare support features and try-on checks.