Estimate a transparent US, UK, or EU starting size from snug underbust and standing bust measurements, view correct sister steps, and verify brand-specific fit.
A quick decision brief for this specific tool
Snug level underbust and standing full-bust measurements in inches plus the label system to use as a starting reference
A transparent measurement-based starting size, rounded band/cup step, nearby sister trials, and an explicit fit decision checklist
Round the underbust to the nearest even band, map rounded bust-minus-band inches to the selected cup progression, and move one band step with one opposite cup step for sister trials
Choose your path
Provide a transparent two-measurement starting size and nearby sister trials, then route the user to exact brand/product fit checks.
Understand how the starting band and cup step are formed.
Measure snug underbust and standing bust, choose a label system, and inspect the calculation.
Uses the result as a try-on starting point rather than a guaranteed size.
Avoid assuming cup letters convert identically.
Choose the actual product’s label system and verify its chart and progression.
Does not carry one cup letter across systems or brands without checking.
Evaluate more than the printed size.
Try the start and nearby sister option, then check band, wire/center, cups, straps and movement comfort.
Rejects painful or visibly poor fit and seeks appropriate fitting/clinical help when needed.
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
Tools you might need next
Convert finger circumference or round-ring inside diameter into an ISO-style millimeter size and nearest U.S. reference, with profile and jeweller checks.
Measure both standing feet, use the larger length and Mondopoint reference, then verify the exact maker/model chart instead of assuming universal size labels.
Calculate anchor size and rode length from boat length, weight, and conditions. Select ground tackle for safe anchoring in varied wind and bottom.
A level snug underbust is rounded to the nearest even UK/US band. EU display uses the corresponding 5-step label rather than converting the body girth directly to centimeters.
UK/US band = round(underbust ÷ 2) × 2Standing bust minus starting band is rounded to a cup index, then looked up in the selected US, UK, or EU progression so later letters are not silently conflated.
Cup index = round(standing bust − starting band)Band-up moves one cup step down and band-down moves one cup step up. These are try-on candidates, not guaranteed equal-volume or equal-shape products.
Updated: August 2026
A shopper obtains a 32D US starting point, sees the underlying four-inch step, and checks the exact product chart before ordering.
A wearer selects the product’s UK or EU labeling system instead of assuming the same later cup letters mean the same thing.
A wearer compares the starting size and one sister trial, then evaluates band, center/wire, cup, strap and movement comfort on the actual garment.
Use the selected system’s band relationship; do not print raw underbust centimeters as the EU band label.
Move a UK/US band by two inches and one cup step in the opposite direction for the adjacent sister trial.
This two-measurement model produces a starting size, not a universal truth. It shows the rounded band, cup step and nearby sister trials, then requires the exact brand/product chart and a real fit check covering band, center/wires, cups, straps and movement comfort.