Finding vintage bras that fit starts with understanding that a labeled 34B (or whatever) from the 1940s, 1950s, 1960s, 1970s or 1980s is rarely identical in band tension, cup volume or shape to a modern 34B. This expanded guide goes deeper into conversions, explains why the numbers shifted, and covers how major brands of the era typically sized their bras so you can shop confidently using your current modern size as a reference.
Core Reasons Vintage Sizes Differ from Modern Ones
The plus-4 (or plus-5) measurement system dominated through the 1940s–1960s and lingered into the 1970s. Women measured their underbust (ribcage) and added 4 or 5 inches to arrive at the band number. Cups were then calculated from the difference to the fullest bust measurement. This compensated for low-stretch or non-stretch fabrics (cotton, early nylon, satin). Modern bras use elastic and power mesh designed to fit snugly at the true underbust measurement with little or no added inches.
Result: The same body often wore a larger band and smaller cup letter in vintage eras. A modern 32D wearer, for example, might have been sized as a vintage 36B under the old method.
Cup volume and depth increased over time. Early lettered cups (A–D introduced in the early-to-mid 1930s) were generally shallower. Absolute volume for a given letter grew as designs evolved, average body sizes changed, and manufacturers responded to demand for fuller coverage. A vintage 34B typically holds noticeably less tissue than a modern 34B. Exact milliliters vary by brand and style, but the trend is consistent: same letter today equals deeper, higher-capacity cups.
Shape differences affect perceived fit more than pure volume. 1940s–1950s bras often created a high, separated, conical or pointed silhouette (bullet bras). 1960s styles softened. 1970s–1980s moved toward more natural or molded rounded shapes closer to today’s. Even if volume matches, the projection and separation feel different.
No universal standard existed. Each manufacturer graded its own patterns, so a 34B Maidenform could differ from a 34B Warner’s or Bali of the same year.
Detailed Size Conversion Guidelines by Decade
Use these as starting points only. Always prioritize actual measurements (snug underbust + fullest bust) and try sister sizes. Sister sizing keeps cup volume roughly the same while changing the band: go up one band and down one cup letter (or the reverse).
1940s conversions
Measurement was strongly plus-4 oriented. Cups were shallow and structured for lift and separation. Modern 32A/B → try vintage 34A or 32A/B
Modern 32C/D → try vintage 34B/C or 36A/B
Modern 34B → try vintage 36A/B or 34B/C
Modern 34C/D → try vintage 36B/C or 38A/B
Modern 36C → try vintage 38B/C or 36C/D
Expect firmer bands and smaller absolute cup capacity. Longline styles (common then) add extra torso coverage that many modern wearers find supportive.
1950s conversions
Peak of the bullet/conical bra. Concentric stitching created dramatic points. Underwires more common. Plus-4 still standard. Volumes remained modest. Modern 32B → try vintage 34A/B
Modern 34B → try vintage 36B or 34C
Modern 34C → try vintage 36C or 38B
Modern 36D → try vintage 38C/D or 40B/C
Pointed cups require the breast tissue to fill the tip for the intended silhouette. Soft or projected modern shapes may need a larger cup letter or different style within the decade.
1960s conversions
Stretch began increasing. Shapes rounded slightly while retaining structure. Still limited primarily to A–D (occasional DD). Modern 32C → try vintage 34B/C
Modern 34B → try vintage 34B/C or 36A/B
Modern 34D → try vintage 36C/D
Modern 36C → try vintage 36C/D or 38B/C
Closer to modern but still often one band larger / one cup smaller as a safe starting range.
1970s conversions
More elastic in bands and cups. Natural shapes and early comfort styles appeared. Cup ranges expanded modestly. Plus-4 influence faded. Modern 34B ≈ vintage 34B (often true or very close)
Modern 34C → try vintage 34C or 36B
Modern 36D → try vintage 36D or 38C
Differences are smaller; many modern 34B wearers succeed in true-to-label 1970s 34B bras, adjusting only for individual stretch loss.
1980s conversions
Most similar to modern. Molded cups, widespread underwire, better stretch. Larger cups more available in some lines. Modern 34B ≈ vintage 34B in most cases
Modern 34DD → try vintage 34DD or 36D
Fit is frequently interchangeable, with remaining differences mainly in shape (less rounded projection in some styles) and elastic recovery after decades of wear.
General conversion formula for quick reference
Take your modern underbust measurement.
For 1940s–early 1960s pieces, add 2–4 inches as a mental starting band and reduce the cup letter accordingly.
Calculate sister sizes around that starting point.
For later 1970s–1980s, start with your exact modern size and test one sister size in each direction.
Brand-Specific Sizing Notes for Common Vintage Bras
Brands graded independently, so these are observed tendencies based on construction, popularity and period practices rather than rigid charts.
Maidenform
Extremely popular across decades (Chansonette, Pre-Lude and many others). Known for structured, well-seamed cups that created defined shapes. 1940s–1950s pieces often feel firm and run true to the era’s smaller cup volumes. Many wearers find Maidenform of this period requires going up a band or adjusting cup relative to modern size. Later 1970s–1980s Maidenform moved closer to modern grading and is frequently wearable at the labeled modern equivalent with minor sister-size tweaks. Longline and strapless styles were strong in their lineup.
Warner’s
Pioneered the Alphabet (A–D) system in the mid-1930s and remained a major player. Early Warner’s bras emphasized volume differentiation within the limited letter range. 1940s–1950s styles tend toward the classic shallower cups and plus-4 friendly bands. They often feel supportive and structured. By the 1970s–1980s Warner’s incorporated more stretch and ran closer to contemporary sizing. Good candidate for true-to-label trials in later decades.Bali
Gained strong reputation for fuller figures and supportive construction, especially mid-century onward. Earlier Bali pieces follow the same smaller-volume, larger-band pattern of the era. Later Bali (1970s–1980s) is frequently recommended for women who need more containment; many modern wearers find Bali of this period runs generous in the cup compared with other vintage brands of the same label, making it useful when converting from a modern fuller cup.
Playtex
Famous for comfort-oriented and early stretch innovations (Cross Your Heart and similar). Playtex often incorporated more elastic earlier than competitors, so their sizing can feel slightly more modern even in 1960s–1970s pieces. Bands may have more give, and cups can accommodate a bit more volume than rigid structured brands of the same decade. Useful when you want a less rigid vintage feel while still staying period-appropriate.
Formfit, Olga, Vanity Fair and similar
Formfit focused on fit standards and supportive shapes in the 1950s. Olga and Vanity Fair (stronger in later decades) leaned toward fashion and comfort. These brands generally followed the same decade-wide trends: shallower cups and plus-4 influence early, closer modern equivalence later. Olga in particular is often noted for consistent construction that many collectors find predictable once they establish their personal conversion for that brand.
Practical brand shopping tip
When a listing names the brand and approximate decade, start with the decade conversion above, then factor brand tendencies (structured brands like early Maidenform or Warner’s = potentially smaller cups; stretchier or full-figure oriented like later Bali or Playtex = potentially more forgiving cups). Measure the actual garment or ask us to provide flat measurements (band stretched vs relaxed, cup depth from underwire or seam to apex).
Extra Tips for Accurate Vintage Bra Fit
Always measure the bra itself when possible: underbust band (relaxed and stretched), cup depth, and wing height.
Elastic degrades. A 1950s band that once measured 34 inches may now stretch further or feel looser. Start on the loosest hooks.
Fill the cups completely for pointed styles; otherwise the silhouette collapses.
Longline and ¾-cup or full-coverage styles common in earlier decades provide more stability for larger modern cups.
Combine with modern sister-size knowledge: the volume relationship (34B ≈ 32C ≈ 36A) still holds across eras.
With these expanded conversions, decade-by-decade adjustments and brand tendencies, you can move beyond guessing and select vintage bras that deliver both authentic period shape and comfortable, supportive fit based on the modern size you already know. Start with one or two well-measured pieces in your calculated range, note what works for your body, and refine from there.
When you're ready for your first (or next) vintage bra and have questions—we can help! Get in touch with us via our CONTACT FORM or send us an email to BillysBras@gmail.com
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