Bra Size Calculator
Example Data Table
| Snug Underbust | Standing Bust | Leaning Bust | Method | Estimated Size |
|---|---|---|---|---|
| 30 in | 36 in | 37 in | Retail plus | 34C |
| 32 in | 39 in | 40 in | Retail plus | 36D |
| 34 in | 42 in | 43 in | Modern snug | 34H |
Formula Used
This calculator first converts all measurements into inches. It creates a weighted underbust value using snug, loose, and tight underbust measurements. The default retail method rounds that value and adds four or five inches to estimate the band. The modern method rounds the weighted underbust to the nearest even band.
The bust value is calculated from standing, leaning, and lying bust measurements. Average shape uses 50% standing, 35% leaning, and 15% lying. Projected shape gives more weight to the leaning value. Shallow shape gives more weight to the standing value.
Cup difference equals rounded bust minus band size. A one inch difference suggests A cup. Two inches suggests B cup. Three inches suggests C cup. The pattern continues through larger cup labels.
How to Use This Calculator
- Choose inches or centimeters.
- Measure snug underbust directly under the bust.
- Add tight and loose underbust values for better accuracy.
- Measure bust while standing, leaning, and lying down.
- Select your preferred fit and sizing method.
- Press the calculate button.
- Review the main result and sister sizes.
- Download the CSV or PDF report if needed.
Bra Sizing and Body Measurement Physics
Why Measurements Change
Bra sizing is based on circumference, stretch, pressure, and cup volume. These are simple physics ideas. A band works like an elastic loop. It stretches around the rib cage and creates support through gentle tension. If the band is too loose, force moves to the straps. That can create shoulder pressure. If the band is too tight, it may dig into soft tissue and feel restrictive.
Why Three Bust Positions Help
Bust tissue moves with posture and gravity. A standing measurement shows the natural relaxed outline. A leaning measurement shows possible cup depth. A lying measurement reduces projection and shows tissue spread. Combining these values gives a better volume estimate than one measurement alone. This is useful when the breast shape is full, shallow, projected, wide set, or uneven.
Band Size and Cup Volume
Cup letters do not have fixed volume by themselves. A 34D and 36C can hold similar volume because cup volume changes with band size. These related choices are called sister sizes. They help when the cup feels right but the band feels wrong. Going down a band usually means going up one cup. Going up a band usually means going down one cup.
Fit Is More Than a Number
A calculator gives a strong starting point. Real fit also depends on fabric, wire width, cup height, strap placement, brand pattern, and personal comfort. Try the suggested size first. Then check the center gore, band level, cup edge, and underwire position. The best size supports your body without pinching, slipping, or leaving empty cup space.
FAQs
1. Is this an official Victoria’s Secret calculator?
No. This is an independent sizing helper. It uses common retail sizing logic and advanced measurement inputs to estimate a useful starting size.
2. Which measurements are required?
Snug underbust and standing bust are required. Tight underbust, loose underbust, leaning bust, and lying bust improve the estimate.
3. What is the retail plus method?
It rounds the underbust and adds four or five inches. This creates a traditional retail band estimate used by many size charts.
4. What is the modern snug method?
It rounds the underbust to the nearest even band. It often gives a firmer band and more direct rib cage support.
5. Why do sister sizes matter?
Sister sizes keep similar cup volume while changing band tightness. They help when the cup feels right but the band feels wrong.
6. Why use leaning and lying bust values?
Different positions reveal tissue projection and spread. The combined average can estimate cup volume better than one bust measurement.
7. Can this calculator replace a fitting?
No calculator can guarantee perfect fit. Use the result as a starting point, then check comfort, support, wire placement, and cup smoothness.
8. Why does the same size fit differently by style?
Brands and styles vary in fabric, wire shape, cup height, padding, and band stretch. Always test the final fit on your body.