Quick start
- Measure underbust in inches.
- Measure around the fullest bust point in inches.
- Calculate to get a starting band and cup estimate.
Best uses
These are the situations this tool is meant for. If your task is close to one of these, the examples and notes below can help you choose the right inputs.
- Get a quick starting size before checking brand charts.
- Understand the difference between band size and cup difference.
- Compare nearby sizes before trying bras on.
- Avoid treating a single measurement as a final fit answer.
What this calculator is solving
The Bra Size Calculator gives a practical starting point from two measurements. It helps explain band and cup math, while making it clear that real fit depends on brand, style, and body shape.
You do not need to memorize the formula first. Start by matching each input label on the calculator to the number, date, unit, or setting you actually have.
The formula in plain language
In plain language: The calculator rounds underbust up to an even band size, subtracts band size from bust size, and maps the difference to an approximate cup label. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
If that sounds abstract, use the example cards on the calculator page. They show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the headline result first. Then look at the smaller supporting lines because they explain the parts behind the answer, such as totals, units, ranges, or formula steps.
- Band is based on the underbust measurement rounded to an even size.
- Cup is based on the difference between bust and band.
- The tolerance note matters because the same label can fit differently across brands.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: the wrong unit, date, weight, scale, mode, or policy assumption.
- Do not treat the estimate as a guaranteed size.
- Do not pull the tape so tight that the measurement changes.
- Check brand size charts and nearby sister sizes before buying.
Research and references
This guide is based on the calculator inputs, the formula note on the tool page, and common school or everyday usage patterns. If your school, workplace, or organization has an official rule, use that rule first.
Examples from the calculator
About 32D
About 34B
Starting size estimate
FAQ in plain language
When should I use the Bra Size Calculator?
Use it when your task matches one of these common needs: Get a quick starting size before checking brand charts. Understand the difference between band size and cup difference. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Bra Size Calculator doing with my inputs?
In plain language: The calculator rounds underbust up to an even band size, subtracts band size from bust size, and maps the difference to an approximate cup label. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
Bra sizing varies by brand, body shape, country, and style. Use this as a fitting starting point, not a guaranteed size. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Related tools
- Body Type Calculator Estimate body shape category from shoulder, bust, waist, and hip measurements.
- Body Surface Area Calculator Estimate body surface area with Mosteller and Du Bois formulas.
- Conversion Calculator Convert length, mass, volume, and temperature units with clear formula steps.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to paste the expression and result into notes, homework, a message, or another document. Check the units and assumptions before copying.