Bikini Size and Body Shape Calculator
Enter your bust, underbust, waist, high-hip, and hip measurements to get your US swimwear letter size for top and bottom, your cup-sized bikini top size, your body shape (one of 7 types), and style recommendations tailored to your figure. Switch between inches and centimetres at any time.
What does this bikini calculator tell you?
This calculator does four things at once. First, it classifies your body shape into one of seven standard types (hourglass, top hourglass, bottom hourglass, spoon, triangle, inverted triangle, or rectangle) based on the proportional relationships between your bust, waist, high hip, and full hip. Second, it recommends a US letter size (XS through 3XL) for your bikini top and bottom separately, because these two pieces often fit best in different sizes. Third, if you enter your underbust measurement, it calculates a cup-sized top size (e.g. 34C or 36DD) for structured and underwire tops. Fourth, it gives you style advice, specific top and bottom styles that flatter your shape, plus what to avoid.
How to take accurate measurements
Use a flexible fabric tape measure and stand naturally with feet together, breathing normally. Bust (overbust): wrap the tape around the fullest part of your chest at nipple level, keeping it parallel to the floor. Underbust: measure snugly around your ribcage directly below your bust, where your bra band sits. Waist: find the narrowest point of your torso, usually an inch or two above your navel. High hip: measure around the top of the hip curve, roughly 4 inches (10 cm) below your waist. This reading helps identify the spoon body shape. Hips: measure around the widest point of your hips and seat. Take each measurement twice and average them if the readings differ slightly. Wear thin clothing or no clothing for accuracy.
Body shapes and what they mean for swimwear
Body shape classification groups your proportions by the ratio of your bust to hips and how defined your waist is relative to both. An hourglass has bust and hips within about 5 percent of each other and a clearly narrower waist. A top hourglass has a larger bust than hips; a bottom hourglass (pear) has wider hips. A spoon is similar to a pear but with a pronounced shelf at the high hip. A triangle has wider hips without a strongly defined waist. An inverted triangle has broader bust than hips. A rectangle has similar measurements throughout with no sharp curves. The goal of swimwear styling is visual balance - using cuts, colors, patterns, and structural features to make proportions look even and harmonious. No shape is better than another; the tips here simply help you find styles that work with your natural lines.
Cup sizing for bikini tops
Most swimwear brands sell standard tops in XS-3XL, but many also offer cup-sized tops - particularly underwire styles, molded-cup designs, and sports tops - in the same band-plus-cup format as bras (e.g. 34C, 36DD). To find your cup size, subtract your underbust measurement from your bust measurement: 1 inch of difference = A cup, 2 inches = B, 3 = C, 4 = D, 5 = DD, 6 = DDD or E. Your band size is your underbust rounded up to the nearest even number. If you plan active water sports, some fitters recommend sizing down one band (e.g. 34 to 32) for a more secure fit, since swimwear fabric relaxes when wet. Sister sizes (same cup volume, different band) are also helpful if the exact size is unavailable.
Why top and bottom sizes often differ
Swimwear tops are sized primarily by bust measurement, while bottoms are sized by hips and waist. Many women find that these two measurements fall into different size brackets. Buying separates rather than a set is the most reliable way to get a true fit on both pieces. As a rough guide, if your hip falls into the next size bracket above your bust, order your top in the smaller size and your bottom in the larger. The reverse applies when your bust is proportionally larger. This calculator compares both measurements and shows the sizes separately when they differ.
Swimwear sizing across brands and international markets
The US size chart used here follows ASTM D5585 apparel standards and is a good starting point, but brands run anywhere from half a size to a full size different, especially European and Australian labels. UK numeric sizes match US sizes closely. Australian sizes are about 2-4 numbers higher than US (AU 12 is roughly US 8, AU 14 is US 10). European sizes (EU) are listed in the chart. Italian and French labels often run smaller than the EU standard. Swimwear fabric stretches 10-20 percent when wet, so a snug-but-comfortable dry fit is usually ideal. Always check the specific brand size guide before purchasing.
US swimwear size chart with international equivalents
| US size | Bust (in) | Waist (in) | Hips (in) | Bust (cm) | Hips (cm) | UK / EU | AU size |
|---|---|---|---|---|---|---|---|
| XS (0-2) | 30-32.5 | 22-24 | 32-34.5 | 76-82 | 81-88 | XS / EU 32 | AU 6-8 |
| S (4-6) | 32.5-34.5 | 24.5-26 | 34.5-36.5 | 82-88 | 88-93 | S / EU 36 | AU 8-10 |
| M (8-10) | 34.5-36.5 | 26.5-28 | 36.5-38.5 | 88-93 | 93-98 | M / EU 38 | AU 12 |
| L (12-14) | 36.5-38.5 | 28.5-30.5 | 38.5-40.5 | 93-98 | 98-103 | L / EU 40 | AU 14 |
| XL (16-18) | 38.5-41.5 | 31-33.5 | 40.5-43.5 | 98-105 | 103-110 | XL / EU 42 | AU 16 |
| 2XL (20-22) | 41.5-44.5 | 34-37 | 43.5-46.5 | 105-113 | 110-118 | 2XL / EU 44 | AU 18 |
| 3XL (24-26) | 44.5-48 | 37.5-41 | 46.5-50 | 113-122 | 118-127 | 3XL / EU 46 | AU 20 |
Approximate body measurement ranges for US swimwear letter sizes. Individual brands may vary by 0.5-1 inch. UK numeric sizes match US sizes closely.
Frequently asked questions
What measurements do I need for the bikini calculator?
You need four required measurements: bust (around the fullest part of your chest), waist (around the narrowest part of your torso), high hip (around the top of the hip curve, about 4 inches below the waist), and hips (around the widest point). The underbust measurement is optional but enables the cup-sized top result. Use a flexible tape and keep it parallel to the floor for each measurement.
Why does my top size differ from my bottom size?
Bikini tops are sized by bust and bottoms by hips, and these two measurements often fall into different size brackets. This is completely normal - most swimwear brands sell tops and bottoms separately for exactly this reason. Order each piece in the size that fits that part of your body rather than trying to find one size that fits both.
What is the high-hip measurement and why is it needed?
The high hip is measured around the top of the hip curve, roughly 4 inches (10 cm) below your natural waist. It helps distinguish the spoon body shape, which has a pronounced hip shelf at this level, from the pear or triangle shapes. If you skip this measurement, the calculator defaults it to your main hip reading, which works for most shapes but may misclassify a spoon figure.
How do I find my cup-sized bikini top size?
Enter your underbust measurement in the optional field. The calculator subtracts underbust from bust to get the cup (1 inch = A, 2 = B, 3 = C, 4 = D, 5 = DD) and rounds your underbust up to the nearest even number for the band. For example, a 34-inch bust and 30-inch underbust gives a difference of 4 inches = D cup, with a band of 30 rounded to 30, so the result is 30D. This format is useful for underwire or molded-cup tops that use bra-like sizing.
Should I size differently for active water sports?
Yes, a more secure fit is advisable. Swimwear fabrics relax when wet, which can loosen a looser style. For active sports, choose tops with wider straps, underwire, cross-back, or racerback construction. The calculator applies a one-band-down adjustment when you select "active / water sports" in the activity field. In letter sizing, opting for a snug M rather than a loose L is a common approach.
How do I choose the best bikini style for my body shape?
The goal is to balance your proportions visually. Hourglass figures work in almost any style. Pear and bottom-hourglass shapes benefit from bold or bright tops that draw the eye upward and simpler, darker bottoms. Inverted-triangle shapes work best with minimal-detail tops and ruffled or embellished bottoms. Rectangle shapes can add the appearance of curves with push-up tops and side-tie or ruffled bottoms. The insight panel above gives tailored recommendations once your measurements are entered.
Are the US sizes accurate for European and Australian swimwear?
The chart is based on US sizing (ASTM standards). European sizes (EU) are shown in the reference table - EU 38 is roughly equivalent to US M. Australian sizes run about 2-4 numbers higher than US (AU 12 is roughly US 8, AU 14 is US 10). UK numeric sizes closely match US numeric sizes. Always cross-reference with the specific brand size guide, as manufacturers vary.
Can I use centimetres instead of inches?
Yes. Switch the unit selector at the top of the calculator to centimetres. All measurement fields update to accept cm, and the calculator converts internally before applying the sizing table. The reference table at the bottom of this page shows both inch and centimetre values for each size bracket.