ABTF Bra Size CalculatorSix measurements. Smarter starting sizes.
Feed in the full ABTF measuring set—loose, snug, and tight ribcage plus standing, leaning, and lying bust—and instantly get band and cup suggestions across US, UK, EU, FR, IT, JP, and AU sizing. No scraped UI, no copied code: everything here is built and tuned for our platform.
- 1Tailored band picks that adjust for ribcage flexibility instead of locking to one number.
- 2Projection-aware cup guidance inferred from the standing/leaning/lying trio.
- 3Instant cross-system conversions, sister sizes, and styling prompts to guide your fitting session.
What makes this different?
Unlike a single-measurement calculator, our ABTF build weighs how compressible your ribcage is, how much lift you need when leaning, and how your tissue rests when supported. It then produces a try-on list plus cross-system conversions you can send straight to our brand tools.
Measurement-first interface
Clean layout, inline validation, and optional cm/in toggles keep the focus on accuracy.
Integrated follow-up tools
Jump directly to brand conversions, sister sizes, fit checks, and style recommendations without retyping data.
Inclusive by design
Supports AFAB/AMAB measurement context, higher cup letters, and bands from 26–52 inches (or 60–120 cm).
How to take ABTF measurements
The ABTF approach relies on consistent tape placement and posture changes. Work through the six checkpoints in order, jotting each value before moving to the calculator below. Measuring on bare skin (or an unlined, non-padded bra) keeps the numbers truthful.
Loose underbust
Relax shoulders and measure where the band sits. This sets the comfort ceiling for your band size.
Snug underbust
Pull the tape evenly but not painfully tight. This value anchors the true band number in the ABTF method.
Tight underbust
Exhale and tighten the tape as much as tolerable. Helps the algorithm read firm ribcages versus compressible torsos.
Standing bust
Measure across the fullest point while standing tall. Captures everyday volume.
Leaning bust
Bend forward 90°. This shows how much tissue needs projection and informs cup depth.
Lying bust
Lie back and measure again. Highlights tissue distribution and support needs.
ABTF Bra Size Calculator
Advanced Mode (ABTF-style)
Use snug/tight underbust and standing/leaning/lying bust to get a recommended try-on range and style tips.
Measurement Guide
Band Size
Measure around your ribcage, just below your breasts. The tape should be snug but not tight.
Bust Size
Measure around the fullest part of your breasts, keeping the tape measure parallel to the floor.
After you get your range
Treat the results as a curated try-on list. Bands may still need micro-adjustments by brand, and cups may flex based on style. Use these follow-up tools to lock in the fit:
- Brand Size ConverterShift your ABTF pick into specific brand labels instantly.
- Sister Size ExplorerSee the up/down band swaps to keep cup volume stable.
- Fit Check WizardTroubleshoot quad-boob, gaping, band riding, and straps within minutes.
- Style RecommenderMatch your new size to plunge, balconette, full cup, or wireless options.
Pro tips for reliable inputs
- Measure twice. Take each value at least twice, averaging if numbers differ more than 0.5 in (1.3 cm).
- Keep the tape flat. Wrinkles or diagonal placement warp the calculations more than you think.
- Use a mirror or helper. Especially for leaning and lying bust readings where the tape can slip.
- Log context. Note hormonal cycle stage or recent weight changes so you can compare like-for-like later.
- Stay relaxed. Holding your breath or pinching the tape sabotages the snug/tight comparison.
Professional Bra Measurement Guide
Essential Tools for Accurate Measurement
Required Equipment
- Soft measuring tape (preferably in inches)
- Non-padded bra or no bra
- Full-length mirror
- Notepad for recording measurements
Measurement Preparation
- Stand straight with shoulders relaxed
- Wear a non-padded bra or no bra
- Ensure the measuring tape is parallel to the floor
- Take measurements in a well-lit room
Step-by-Step Measurement Guide
Band Size Measurement
- Measure under your bust, where the bra band sits
- Keep the tape snug but not tight
- Ensure the tape is parallel to the floor
- Round to the nearest even number
Bust Size Measurement
- Measure around the fullest part of your bust
- Keep the tape parallel to the floor
- Don't pull the tape too tight
- Record the measurement in inches
Cup Size Calculation
- Subtract band size from bust measurement
- Use the difference to determine cup size
- Each inch difference represents one cup size
- Example: 1" = A, 2" = B, 3" = C, etc.
Professional Tips for Accurate Results
Common Measurement Mistakes
- Measuring over a padded bra
- Pulling the tape too tight
- Not keeping the tape parallel to the floor
- Measuring at the wrong position
Professional Recommendations
- Take measurements at least twice for accuracy
- Measure at the same time each day
- Consider professional fitting for best results
- Update measurements every 6 months
This page references the community-developed A Bra That Fits measuring philosophy. All wording, interface design, and calculation code are original to this site. Use the results as guidance and verify fit with real try-ons.