Best for turning bust and underbust measurements into a practical starting size.

Bra Size Calculator

Enter your bust and underbust measurements to estimate a starting bra size across US, UK, EU, and FR systems, then compare the result with the brand's own chart.

量測並建議尺寸

輸入自己的數據，系統會找出最接近的參考列，再依品牌尺寸表確認。

怎麼量

內衣

下胸圍水平貼合身體，保持貼身但不勒。
胸圍量最豐滿的位置。
用胸圍和下胸圍差值看罩杯，再核對品牌算法。

你的數據

單位

下胸圍

胸圍 / 胸部

最接近參考

先輸入你已有的數據。只填一部分也可以，欄位越完整越接近。

僅供參考。版型、寬度、材質、鬆量和品牌規則都會影響最後選擇。

量測細節

使用軟尺，穿無襯墊或輕薄內衣量測。軟尺保持水平，正常呼吸，不要刻意收緊。

下胸圍 / Band

軟尺繞過胸下、內衣下圍所在的位置，貼合身體並保持一圈水平。

多數尺寸體系會用它來確定 band 數字。

胸圍 / Overbust

軟尺繞過胸部最豐滿的位置，不要壓扁胸部，也不要讓背後下墜。

站在鏡子前量更容易保持水平。

罩杯差值

胸圍減下胸圍得到差值，再用差值去參考罩杯。不同地區 D 以後寫法會不一樣。

罩杯字母不能脫離 band 單獨理解。

合身檢查

下圍應提供主要支撐，杯面不空杯也不壓杯，肩帶不應承擔全部重量。

如果下圍合適但杯量不對，可以再看姊妹尺寸。

下胸圍 / 圍度參考

先用下胸圍對照常見 US、UK、EU、FR 圍度標示，再搭配品牌的取整方式確認。

下胸圍	下胸圍 (cm)	US 圍度	UK 圍度	EU 圍度	FR 圍度
21-22 in	53-57 cm	26	26	55	70
23-24 in	58-62 cm	28	28	60	75
25-26 in	63-67 cm	30	30	65	80
27-28 in	68-72 cm	32	32	70	85
29-30 in	73-77 cm	34	34	75	90
31-32 in	78-82 cm	36	36	80	95
33-34 in	83-87 cm	38	38	85	100
35-36 in	88-92 cm	40	40	90	105
37-38 in	93-97 cm	42	42	95	110
39-40 in	98-102 cm	44	44	100	115
41-42 in	103-107 cm	46	46	105	120
43-44 in	108-112 cm	48	48	110	125
45-46 in	113-117 cm	50	50	115	130
47-48 in	118-122 cm	52	52	120	135
49-50 in	123-127 cm	54	54	125	140
51-52 in	128-132 cm	56	56	130	145

罩杯 A / B / C / D 參考

用胸圍減下胸圍得到罩杯差，再對照 A、B、C、D 以及更大的罩杯標示。罩杯字母不能脫離圍度單獨判斷。

差值	差值 (cm)	US 罩杯	UK 罩杯	EU 罩杯
1 in	2.5 cm	A	A	A
2 in	5 cm	B	B	B
3 in	7.5 cm	C	C	C
4 in	10 cm	D	D	D
5 in	12.5 cm	DD/E	DD	E
6 in	15 cm	DDD/F	E	F
7 in	17.5 cm	G	F	G
8 in	20 cm	H	FF	H
9 in	22.5 cm	I	G	I
10 in	25 cm	J	GG	J
11 in	27.5 cm	K	H	K
12 in	30 cm	L	HH	L
13 in	32.5 cm	M	J	M
14 in	35 cm	N	JJ	N

How to Use the Bra Size Calculator

Choose inches or centimeters, measure directly under the bust for the underbust value, and measure around the fullest part of the bust. Enter both values without pulling the tape too tightly. The calculator maps the measurements to a practical band and cup reference rather than making a body-shape assessment.

How Band and Cup Size Are Estimated

The band estimate starts with the underbust measurement. The cup estimate uses the difference between bust and underbust measurements. Because regional labels and brand rounding rules differ, the result includes multiple sizing systems and should be checked against the exact product chart.

US, UK, EU, and FR Bra Size Results

US and UK band labels are commonly shown in inches, while EU and FR labels use different numeric conventions. Cup progressions can also diverge after D. Treat the combined band and cup result as a translation aid when comparing international stores, not as a universal conversion guarantee.

Check Fit Before Buying

A calculated size cannot account for every brand, garment construction, material, or fit preference. Confirm that the band remains level and comfortable, the cup edge sits smoothly, and the product's return policy is suitable. For pain, post-surgery needs, pregnancy, or medical concerns, consult a qualified professional.

常見問題

What measurements do I need for the bra size calculator?

You need an underbust measurement and a bust measurement taken around the fullest part of the bust.

Can I calculate bra size in centimeters?

Yes. Select centimeters before entering the measurements; the calculator converts them for the same reference logic.

Does the calculator show international bra sizes?

Yes. It returns starting references for common US, UK, EU, and FR band and cup labels.

Is the calculated bra size exact for every brand?

Use the result as a sizing reference, then check the brand or seller chart before buying. Materials, fit preference, country labels, and manufacturing tolerances can change the best choice.