How Accurate These Tools Are, Honestly
Every result on this site is an approximation. That is not a hedge added for legal comfort — it is the actual situation, and this page sets out how large the approximation is for each kind of tool. Clothing sizing in particular is far less consistent than most people assume: the same labelled size varies by several centimetres between brands, and sometimes within one.
In Plain Terms
Each of those is explained below, with figures.
Why the Same Size Is Not the Same Size
Most people arrive at a size converter assuming the difficulty is the conversion — turning a UK 12 into a European 40. That part is straightforward and the arithmetic is exact. The difficulty is that a size 12 is not a fixed measurement in the first place.
Clothing sizes are not a standard that brands follow. Each brand picks a base size, decides the measurements for it, and grades every other size up or down from there by increments it chooses. Two brands can both call a garment a 12 and mean waist measurements several centimetres apart. Neither is wrong, because there is no authority either is departing from.
That variation is not random and it is not small. Across the European and British high street, the waist measurement on a garment labelled size 12 commonly spans a range of seven centimetres between the narrowest brand and the most generous (from 72 cm at Max Mara to 79 cm at Mango). That is more than a full size in most brands' own grading. It is why someone can be a 10 in one shop and a 14 in another and both be correct.
This is what the brand deviation tables on the sizing pages exist for. They record, brand by brand, which labels run small, which run large and which sit close to their published charts. They are the most useful part of those tools and the part that needs the most frequent updating.
Waist measurement for a size 12 across 10 high-street brands
Each of these brands calls this garment a size 12. None of them is wrong, because there is no standard either is departing from. Figures from each brand's own published size guide, checked September 2026.
View accessible text data for this chart
Waist measurements for size 12 across 10 high-street brands (7 cm spread):
- Max Mara: 72 cm (narrowest)
- Uniqlo Europe: 73 cm
- Zara: 74 cm
- Massimo Dutti: 74 cm
- Sézane: 75 cm
- COS: 76 cm
- H&M: 76 cm
- & Other Stories: 76 cm
- Arket: 77 cm
- Mango: 79 cm (most generous)
Range spans 72 cm to 79 cm — exactly 7 cm between the narrowest and most generous brand.
What this means for a converter result
A conversion tells you what your measurement corresponds to in another system. It cannot tell you what a specific brand will call that measurement, because only that brand decides. Take the converted size as a starting point, then check the brand's own chart — which is definitive for their garments in a way that no third-party tool can be.
How Far Out Each Kind of Tool Can Be
The nineteen tools do different things and their error ranges differ accordingly. Treating a measurement conversion and a style quiz as equally certain is the mistake this table exists to prevent. Each tool's own page states the limitations specific to it, in more detail than this.
| TOOL TYPE | HOW CLOSE | WHAT MOVES IT | WHAT TO DO |
|---|---|---|---|
| Size conversions | Arithmetic exact; garment varies by up to a full size | Brand grading, fabric, cut | Check the brand's own chart before buying |
| Ring, hat and glove sizing | Within half a size, given a careful measurement | How the tape sits, time of day, temperature | Measure twice; try on where possible |
| Bra sizing | Within one band or cup, often more | Brand, style, wear on the garment | A starting point only; fit varies enormously by style |
| Body and face shape | Boundaries are conventions, not standards | Where you sit relative to a threshold | Read the neighbouring category too |
| Colour season and undertone | An informed categorisation, not a measurement | Light, makeup, recent tanning, hair colour | A professional draping is meaningfully more accurate |
| Cost per wear and budget | Arithmetic exact; your inputs are estimates | Your own guess at future wear, which is usually generous | Use comparatively, between two options |
| Luggage weight | Within roughly half a kilo on a full bag | Fabric weights, what you add at the last minute | Weigh the bag if you are near a limit |
| Outfit and palette generators | Suggestions, not verdicts | Nothing — deterministic, but still suggestions | React to them rather than following them |
Where a figure here and a tool page disagree, the tool page is more specific and is correct.
Why we publish these ranges
Because a tool that claims precision it does not have is worse than one that states its uncertainty. Every tool here shows its formula or its thresholds, which means you can see exactly what produced your result and judge for yourself how much weight it deserves. That is unusual in this category and it is deliberate.
When to Check a Result, and How
Short answer: Check whenever the cost of being wrong is more than the cost of checking. For a ten-pound t-shirt, the tool is enough. For a coat, a pair of boots, an alteration or a bag close to an airline limit, spend the two minutes.
Verification is not a ritual and does not need doing every time. The useful rule is proportional: how much does it cost if the result is out by one size or half a kilo. Most of the time the answer is a return and some inconvenience. Sometimes it is a fee at a check-in desk or a garment that cannot be sent back.
For clothing, the definitive source is the brand's own size guide, published on their website in the measurements they actually grade to. Our conversion gives you a measurement; their chart tells you what they call it. Where a brand publishes garment measurements rather than body measurements — increasingly common — those are more useful still, because they describe the thing rather than the wearer.
For anything with a physical answer, the physical answer wins. A scale beats a luggage calculator. A tape measure beats a remembered figure. A garment held against you beats any chart. None of the tools here would claim otherwise, and several say so on their own pages.
Under about thirty pounds
The tool is usually enough. A return is the worst case.
A significant garment
Check the brand's chart. Two minutes against a coat you will keep for years.
Anything non-returnable
Sale items, alterations, made-to-measure. Verify before committing.
Near an airline limit
Weigh it. A calculator estimates; a scale measures.
If a tool and reality disagree
Reality is right. If the calculator says one thing and the garment in your hands says another, trust the garment.
What These Tools Are Not
Several tools touch subjects where a confident answer from an unqualified source could do harm. Each tool's page states the boundary that applies to it; they are collected here because a reader looking for a disclaimer will reasonably expect to find them in one place.
Not medical or health information
The body shape calculator, the measurement tools and the undertone test describe proportions and colouring for choosing clothes. None of them is health information. Nothing here provides nutrition, fitness, dermatological or diagnostic guidance, and no result carries any information about your health. Body shape categories describe where width sits on a frame and nothing more.
Not financial advice
The cost per wear and clothing budget tools organise one category of spending. They do not advise on debt, savings or household finances, do not assess affordability, and are not regulated financial advice in any jurisdiction.
Not a substitute for a professional
A trained colourist with physical drapes under controlled light is meaningfully more accurate than any colour quiz. A fitter with a tape measure beats any size chart. A tailor solves problems no converter can. Several pages say this outright and note when the cost is worth it.
Not a guarantee of fit
No tool on this site can see the garment you are considering. A result narrows the field; it does not promise that a particular item from a particular brand will fit you.
The legal position on liability is set out in the terms and conditions. This page describes the practical one.
When Something Here Is Simply Wrong
Approximation is one thing and error is another. The ranges above describe how far a correct tool can be from a particular garment. They do not cover a figure that is actually wrong — a conversion mis-typed, a brand note left unchanged after the brand revised its chart, an arithmetic mistake.
Those happen. One person maintaining several thousand figures across nineteen tools will get some of them wrong, and brands change grading without announcing it. Report one and it is checked against the source and corrected, with a note on the page stating what changed and when. The note stays rather than being removed later.
Report an error
Email fashion@womensfashioneu.com with the page URL and what is wrong. Include a source if you have one — it makes the check considerably faster. Replies usually within two to three working days.
Changes to This Page
The ranges and the chart on this page will change as the tools and the brand data do. Material changes are posted here with a date.
Change Log
- 20 September 2026 — First published.