Undergarments Fit Lab
Visual fit, sizing and style tools for bras, lingerie, women’s and men’s underwear, shapewear, sports bras, hosiery, base layers and age-appropriate youth/teen basics.
What are you trying to decide?
Bra Fit DiagnosticUse this for the specific bra-sizing task in “Bra Fit Diagnostic” when you need a transparent starting point, conversion or sister-size relationship plus the next fit check.Open tool →Bust & Underbust Measurement VisualizerUse this when you are searching for underbust measurement, bust and underbust measurements, or need to understand where each bra-fitting measurement is taken.Open tool →Bra Sister Size CalculatorUse this for the specific bra-sizing task in “Bra Sister Size Calculator” when you need a transparent starting point, conversion or sister-size relationship plus the next fit check.Open tool →Bra Size ConverterUse this for the specific bra-sizing task in “Bra Size Converter” when you need a transparent starting point, conversion or sister-size relationship plus the next fit check.Open tool →Sports Bra Support FinderUse this for the specific bra-sizing task in “Sports Bra Support Finder” when you need a transparent starting point, conversion or sister-size relationship plus the next fit check.Open tool →Underwear Fit DiagnosticUse this when the question behind “Underwear Fit Diagnostic” is whether a chart range is plausible for you and which fit variable still needs checking.Open tool →Shapewear Coverage & Outfit MatcherUse this when choosing shapewear shorts vs a bodysuit, deciding what works under a fitted or low-back outfit, or wondering whether stronger shaping means sizing down.Open tool →Tights Denier Visual ExplorerUse this when comparing 10, 20, 40, 60, 80 or 100 denier tights and you want a clear visual explanation of what the number can—and cannot—tell you.Open tool →
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Bra Band Size CalculatorBra Band Size Calculator is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Cup Difference CalculatorBra Cup Difference Calculator is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Starting Size CalculatorBra Starting Size Calculator is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Sister Size CalculatorBra Sister Size Calculator is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Sister Size UpBra Sister Size Up is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Sister Size DownBra Sister Size Down is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Size ConverterBra Size Converter is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →US to UK Bra Size GuideUS to UK Bra Size Guide is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →UK to EU Bra Size GuideUK to EU Bra Size Guide is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Band Difference CalculatorBra Band Difference Calculator is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Cup Volume Step ComparatorBra Cup Volume Step Comparator is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Underwear Size HelperUnderwear Size Helper helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Briefs Size HelperBriefs Size Helper helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Boxer Size HelperBoxer Size Helper helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Boxer Brief Size HelperBoxer Brief Size Helper helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Panty Size HelperPanty Size Helper helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Shapewear Size HelperShapewear Size Helper uses your measurements and the current brand range as a sizing check while clearly separating garment size from compression level. It is designed to prevent the common mistake of choosing a smaller size simply to create more shaping.Open →Camisole Size HelperCamisole Size Helper is a focused clothing utility that turns the values you enter into transparent arithmetic and practical decision support. It keeps assumptions visible, explains what the result can and cannot tell you, and directs you to the product-specific measurement, chart or care instruction that should be checked next.Open →Slip Size HelperSlip Size Helper is a focused clothing utility that turns the values you enter into transparent arithmetic and practical decision support. It keeps assumptions visible, explains what the result can and cannot tell you, and directs you to the product-specific measurement, chart or care instruction that should be checked next.Open →Hosiery Size Chart ComparatorHosiery Size Chart Comparator interprets a real hosiery or tights size-chart range using your own inputs, while keeping size designation separate from denier, stretch and opacity. It is meant to highlight where you sit in a product grid rather than invent one universal tights size.Open →Tights Size Chart ComparatorTights Size Chart Comparator interprets a real hosiery or tights size-chart range using your own inputs, while keeping size designation separate from denier, stretch and opacity. It is meant to highlight where you sit in a product grid rather than invent one universal tights size.Open →Sock Size by Foot LengthSock Size by Foot Length is a focused clothing utility that turns the values you enter into transparent arithmetic and practical decision support. It keeps assumptions visible, explains what the result can and cannot tell you, and directs you to the product-specific measurement, chart or care instruction that should be checked next.Open →Undershirt Fit CalculatorUndershirt Fit Calculator is a focused clothing utility that turns the values you enter into transparent arithmetic and practical decision support. It keeps assumptions visible, explains what the result can and cannot tell you, and directs you to the product-specific measurement, chart or care instruction that should be checked next.Open →Thermal Base Layer Fit CalculatorThermal Base Layer Fit Calculator is now a movement-first base-layer fit workspace. It distinguishes a smooth close fit from true compression and helps you check whether the layer stays positioned under movement without bulky folds, pressure or unwanted ride-up.Open →Bust & Underbust Measurement VisualizerA visual measurement workspace that keeps full-bust and underbust circumferences separate, records the exact difference, and explains when that difference is useful without pretending it automatically determines one universal bra cup size.Open →Bra Fit DiagnosticBra Fit Diagnostic is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Bra Style & Construction ExplorerBra Style & Construction Explorer is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Sports Bra Support FinderSports Bra Support Finder is a visual, measurement-aware bra fitting utility. It keeps band, cup and sizing-system logic separate, shows what the result means, and makes the brand chart and observable fit checks explicit instead of presenting one bra label as universally correct.Open →Underwear Fit DiagnosticUnderwear Fit Diagnostic helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Men’s Underwear Style FinderMen’s Underwear Style Finder helps compare a current underwear size chart with the actual waist, hip or garment evidence you have, while keeping rise, leg opening, coverage, stretch and cut in view so a local fit problem is not reduced to one generic size number.Open →Shapewear Coverage & Outfit MatcherShapewear Coverage & Outfit Matcher uses your measurements and the current brand range as a sizing check while clearly separating garment size from compression level. It is designed to prevent the common mistake of choosing a smaller size simply to create more shaping.Open →Tights Denier Visual ExplorerTights Denier Visual Explorer interprets a real hosiery or tights size-chart range using your own inputs, while keeping size designation separate from denier, stretch and opacity. It is meant to highlight where you sit in a product grid rather than invent one universal tights size.Open →Undergarment Style LibraryExplore common undergarment constructions visually and compare what actually changes: rise, rear coverage, leg length, cup construction, support, edge placement, compression and layering role.Open →
Learn the measurement or decision first
How to measure underbust and bustMeasure underbust directly beneath the breast area and full bust around the fullest relevant level, keeping both tape pa…How bra sister sizes workBra sister sizing changes the band and cup letter together to keep a broadly similar cup-volume relationship within the …Why bra size differs by brandUse bra calculators and charts as a starting point built from raw measurements, then assess the actual band, cup contain…How to use a bra size chartUse bra calculators and charts as a starting point built from raw measurements, then assess the actual band, cup contain…US UK and EU bra size differencesUS, UK and EU bra labels are not a single universal sequence. Compare the current brand’s band and cup progression direc…How to choose underwear from waist and hip measurementsChoose underwear using the body waist and/or hip range requested by the brand, then consider rise, elastic tension and f…How to compare shapewear size chartsChoose shapewear from the brand’s current body-measurement chart and intended compression level. Do not size down aggres…How to size tights and hosiery from a brand chartTights and hosiery charts often combine body dimensions such as height and weight or hip/waist ranges. Use the exact var…How to choose a base layer fitFor undergarments and base layers, use the body measurements requested by the current brand and then account for intende…Why intimate apparel calculators should be a starting pointFor undergarments and base layers, use the body measurements requested by the current brand and then account for intende…What is an underbust measurement?Place a flexible tape horizontally around the torso directly beneath the breast area, keep it level at the back, and rec…Bust vs underbust measurementBust and underbust are two different torso circumferences used by bra charts and fitting methods. Underbust is measured …Should you size down in shapewear?No: sizing down is not the correct way to get more shaping. Use the brand’s current size chart for your measurements, th…Why does shapewear roll down?Shapewear can roll because the garment is too small, too large, the waistband height or construction conflicts with your…Shapewear shorts vs bodysuitShapewear shorts add abdomen/hip/thigh coverage, while bodysuits extend shaping through more of the torso and can anchor…Tights denier guide: 10D, 20D, 40D, 80D and beyondThink of denier as yarn weight, not “percent opaque.” A 10D product generally uses finer/lighter yarn than an 80D produc…How do tights size charts work?Tights charts commonly combine height with weight, hip or another body dimension. Use the exact product grid and note wh…How should a base layer fit?A base layer usually works best when it sits close enough to avoid bulky folds under the next layer and stays positioned…