ABTF Calculator – 6-Measurement Method
The "A Bra That Fits" method uses six measurements for the most accurate bra size – especially for larger busts and different breast shapes. Enter your measurements and get your size in US, UK, EU, AU, and FR.
ABTF Bra Size Calculator
Measure underbust without pulling tight – tape should be loose.
Measure underbust snug – tape should be firm but comfortable.
Pull tape as tight as possible – exhale fully.
Measure bust standing – tape level around fullest part.
Lean forward 90° and measure – captures breast projection.
Measure bust while lying flat on your back.
34C
34C
75C
12C
90C
Need a different method? Try the Standard Bra Size Calculator or Sister Size Finder.
What Is the ABTF Method?
The ABTF (A Bra That Fits) method is a community-developed sizing system that uses six measurements – three underbust and three bust – to calculate your most accurate bra size. Unlike standard 2-measurement calculators, ABTF accounts for breast tissue squish, density, and natural projection.
How to Measure for ABTF
📏 Underbust Measurements
Take all three measurements directly under your bust, with the tape level around your ribcage.
- Loose: Tape barely touching – breathe normally.
- Snug: Firm but comfortable – tape stays in place.
- Tight: Pull as tight as possible – exhale fully.
📐 Bust Measurements
Measure around the fullest part of your bust in three positions.
- Standing: Tape level around fullest part.
- Leaning: Bend 90° forward – captures projection.
- Lying: Flat on your back – captures natural shape.
How ABTF Calculates Your Size
The ABTF method uses the average of your three underbust measurements for the band, and the average of your three bust measurements for the cup. This averaging reduces measurement error and gives you a size that fits your body's natural shape.
For example, if your underbust measurements are 33, 32, and 30, the average is 31.7 – rounded to 32 for the band. If your bust measurements average to 36.3, the difference is 4.3 inches – giving you a D cup.
ABTF vs Standard vs Victoria's Secret
| Method | Measurements | Band | Best For |
|---|---|---|---|
| Standard | 2 (underbust, bust) | Rounded even | Quick estimate |
| ABTF | 6 (3 underbust, 3 bust) | Averaged, rounded | Most accurate |
| Victoria's Secret | 2 (+4 method) | Underbust +4 | VS store fitting |
Not sure of your measurements?
Read the Measuring GuideFrequently Asked Questions
Why is ABTF more accurate than standard calculators?
ABTF uses six measurements (three underbust, three bust) instead of two. This averages out measurement errors and accounts for breast tissue squish, density, and natural projection – giving you a size that fits your unique shape.
Do I need to wear a bra when measuring for ABTF?
For best results, measure without a bra or with a non-padded, non-pushup bra. This gives the most accurate measurements of your natural shape.
What if my ABTF size is different from my usual size?
That's common! Many people find ABTF gives a smaller band and larger cup than they're used to. Try the ABTF size – you might find it's more comfortable and supportive.
Does IMRango store my measurements?
No. Everything runs locally in your browser. We do not collect, store, or share any of your personal data or measurements.