Bra Size Calculator – Find Your Perfect Bra Size Free Online

Spluxly’s free online Bra Size Calculator is a precise and practical fitting tool designed to help anyone find their correct bra size quickly and confidently from home. Using just two measurements — your underbust circumference and your bust circumference — the calculator applies standard international sizing charts to instantly determine your band size, cup size, and complete bra size in both imperial format (e.g., 34B) and European metric format (e.g., 75C). Both centimetres and inches are supported, with a simple unit toggle to match your preferred measuring system. Results are displayed in a professionally styled result card alongside a comprehensive breakdown table that shows every step of the calculation including the underbust measurement, bust measurement, the difference between the two, the derived band size, the derived cup size, and the final bra size with a clear description. Built-in measurement guidance explains exactly how to position the tape measure correctly for both the underbust and bust readings, removing the guesswork from the process entirely. Whether you are shopping online, replacing worn-out bras, or simply unsure of your correct size, this calculator delivers accurate results in seconds. Completely free, no registration required.

How to Use the Bra Size Calculator Online

Finding your bra size takes just seconds. Follow these simple steps:

How to Take Your Measurements:

• Underbust – Wrap a soft measuring tape directly under your bust, keeping the tape snug, level, and parallel to the floor all the way around
• Bust – Wrap the tape around the fullest part of your bust, keeping it relaxed and level; do not pull it tight

Calculator Steps:

• Select Your Unit – Choose Centimeters (cm) or Inches (in) from the unit dropdown to match your measuring tape
• Enter Your Underbust Measurement – Type your underbust circumference into the underbust field (e.g., 73.5 cm or 29.0 in)
• Enter Your Bust Measurement – Type your bust circumference into the bust field (e.g., 88.0 cm or 34.5 in)
• Click Calculate Bra Size – Instantly receive your band size, cup size, complete bra size, a styled result card, and a full breakdown table
• Review the Result Card – See your bra size displayed prominently (e.g., 34B or 75C) along with a brief description of what the size means
• Review the Breakdown Table – View all metrics in detail including unit, underbust measurement, bust measurement, difference, band size, cup size, bra size, and description

How Bra Size Is Calculated

Bra size is determined by two separate calculations: one for the band size and one for the cup size.

Band Size Calculation (Inches): The underbust measurement in inches is rounded to the nearest even number to produce the band size. If the underbust measurement is an odd number, it is rounded up to the next even number.

• Underbust 29 in → Band Size 30
• Underbust 31 in → Band Size 32
• Underbust 33 in → Band Size 34

Band Size Calculation (Centimetres): The underbust measurement in cm is mapped to the nearest standard European band size using the conventional metric sizing chart (e.g., 70, 75, 80, 85, 90 cm).

Cup Size Calculation: The cup size is determined by the difference between the bust measurement and the underbust measurement.

Example for underbust 30 in and bust 34 in:

• Band Size: 30 in → 32
• Difference: 34 − 30 = 4 in → Cup D
• Bra Size: 32D

Why Use Spluxly’s Bra Size Calculator?

• Two-Measurement Input – Requires only underbust and bust measurements to calculate a complete bra size, keeping the process simple and accessible without the need for complex multi-point body measurements
• Centimetres and Inches Support – A simple unit toggle accepts measurements in either centimetres or inches, producing results in both standard imperial sizing (e.g., 34B) and European metric sizing (e.g., 75C) simultaneously
• Built-In Measurement Guidance – Clear on-page instructions explain exactly how to position the tape correctly for both the underbust and bust readings, helping users achieve accurate inputs for a reliable result
• Band and Cup Breakdown – The result is not just a single size label; the full breakdown table shows the underbust value, bust value, calculated difference, derived band size, derived cup size, and final combined bra size separately for complete transparency
• Styled Result Card – Your bra size is presented in a clean, professionally styled result card with a brief size description, making the result easy to read and reference while shopping
• Comprehensive Breakdown Table – Every metric involved in the calculation is listed clearly in a dedicated table covering unit, both measurements, difference, band, cup, final size, and description
• 100% Free & Instant – No registration, no fees — your accurate bra size with band size, cup size, and full measurement breakdown delivered in seconds