Health category
Fitness, nutrition, pregnancy, sleep, and wellness calculators.
Bra Size Calculator
Use your underbust and bust measurements to estimate your bra size in US, UK, and EU systems. It also shows nearby sister sizes if you need a tighter or looser band fit.
Measure snugly around your ribcage, directly under your bust.
Measure around the fullest part of your bust while keeping the tape level.
EveryCalc calculators are designed for fast, practical estimates with transparent inputs and no required account. We use plain formulas, visible assumptions, and related tools so visitors can check the result from more than one angle.
Results are informational only. For financial, tax, legal, medical, construction, or other high-impact decisions, verify the output against primary sources or a qualified professional.
Learn more about our review process on the EveryCalc methodology page.
How this calculator works
What this page estimates
This Bra Size Calculator is built to give a quick, browser-based estimate for bra size. Use your underbust and bust measurements to estimate your bra size in US, UK, and EU systems. It also shows nearby sister sizes if you need a tighter or looser band fit. The inputs stay on the page during normal use, and the result should be treated as an estimate for planning, comparison, or education rather than professional advice.
Calculation approach
The calculator applies the standard relationship implied by the inputs, then formats the answer so it can be checked and reused. For health tools, the most important step is using consistent units, rates, time periods, and assumptions before comparing the result with another calculator or outside quote.
Example workflow
For example, start with a realistic value you already know, change one input at a time, and watch how the answer moves. That makes it easier to tell whether the result is being driven by the main amount, the rate, the time period, or a unit conversion.
Practical checks
- Use current, real-world numbers when the result affects money, health, tax, or legal decisions.
- Run a low, base, and high case when the inputs are estimates.
- Check the related calculators below when the next decision depends on a different assumption.
How to interpret the bra size result
Best use
Use the result as an informational wellness estimate that can help organize measurements, targets, or timing before a conversation with a clinician.
Cross-check
Compare the output with your own records, device readings, lab values, medication instructions, or guidance from a qualified health professional.
Watch for
Do not use this page to diagnose, treat, or ignore symptoms. Health calculators are most useful when they make questions clearer, not when they replace care.
This page belongs to the Health calculator library, so the answer should be read in the context of the decision you are modeling rather than as a universal rule.
Before relying on this bra size estimate
Most calculator mistakes come from the inputs, not the arithmetic. Use this short audit before you reuse the answer in a spreadsheet, quote, application, or important conversation.
Use current measurements
Recent weight, height, age, activity, nutrition, sleep, or timing inputs matter more than remembered estimates.
Look for context
A calculator can organize a wellness number, but it cannot read symptoms, medical history, medications, or lab results.
Escalate high-impact questions
Use clinical guidance for pregnancy, dosage, heart, risk, illness, or treatment decisions.
Rerun this page when measurements change, a clinician gives new guidance, or the result is being used for a new goal.
How to Use
- Choose inches or centimeters.
- Measure snugly around your ribcage just below your bust and enter that as your band measurement.
- Measure around the fullest part of your bust and enter that as your bust measurement.
- Review your estimated US, UK, and EU sizes, then compare the suggested sister sizes for fit adjustments.
Frequently Asked Questions
How accurate is a bra size calculator?
A bra size calculator is a useful starting point, but fit can still vary by brand, style, and personal comfort. Use the result as a baseline, then adjust after trying on bras if needed.
What are sister sizes?
Sister sizes keep a similar cup volume while changing the band size. For example, if your usual band feels tight, you can go up one band size and down one cup size for a similar fit.
Why are US and UK bra sizes different?
US and UK sizing use different cup naming systems after D and DD. That is why the same measurements may show a different cup letter depending on the regional size format.
Should I measure in inches or centimeters?
Either is fine. This calculator converts both measurements automatically, so use whichever unit is easier for you.
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