Bra sizing and fit tools
Select the calculation or decision you need. Each tool accepts the inputs for that question and explains its result.
G Cup Bra Size Calculator
Enter underbust and full bust to estimate a starting UK or US size on the homepage.
Calculate a starting size →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.
Use this tool →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.
Use this tool →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.
Use this tool →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.
Use this tool →G Cup Comparison Tool: Band and Cup Sizes
Keep both systems visible. A 34G UK and 34I US align on the same chart; a 34G UK and 36FF UK are adjacent sister sizes.
Use this tool →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.
Use this tool →G Cup Bra Shape and Style Guide
Combine three supported-garment observations into construction features to compare. No size is inferred from an appearance category.
Use this tool →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.
Use this tool →For a starting size and the meaning of G in UK and US systems, use the main G cup bra calculator and explanation.