Let’s talk about one of the least glamorous - yet most critical - parts of product development: grading.
It’s the stage most people never think about.
No mood boards. No fittings. No fabrics to touch. Just… maths.
But if your grading is wrong, every size after your base pattern will be too, and no amount of fit sessions or fabric tweaks will save it.
At its simplest, grading is how you turn one pattern into a full size range.
Each size increases by a set amount so that the garment fits a bigger body without changing its proportions or style.
As a general guide, a garment’s total circumference increases by around 5 cm per size.
That’s a starting point - there’s nuance depending on target customer, curve ranges, vanity sizing and so on - but it’s a solid rule of thumb.
So, if a waistband measures 60 cm in a size 10, it’ll roughly measure 65 cm in a 12, 70 cm in a 14, and so on.
Simple enough in theory. But here’s where things fall apart.
A common mistake happens when brands rely on their factory to handle grading.
Factories often mean well, but they’re working from a technical brief, not a brand perspective, and without guidance, they’ll just “follow orders.”
Here’s what I see time and time again:
A brand fits two sample sizes (say a 10 and an 18).
They give separate comments on each, thinking of them as individual garments rather than two ends of one graded range.
So, they ask the factory to reduce the waist by 1 cm on the size 10, and increase it by 2 cm on the 18.
Sounds harmless.
But now we have two different base patterns.
When the factory later applies a standard 5 cm grade to each, the middle sizes don’t align - and somewhere around the middle, the grade jumps.
In this example, between a 14 and 16 there’s suddenly an 8 cm leap instead of 5.
To the brand, it looks fine on paper.
To the customer, it’s a disaster.
That 8 cm gap might not sound like much - until your customer tries it on.
A size 14 that feels too tight, a size 16 that feels too loose.
They buy one, exchange it, then give up.
Fit inconsistency breaks trust fast - and once you lose that, it’s hard to win back.
Now imagine the same issue in bras, where grading is far more complex.
One brand I worked with had tried to simplify their range by combining cup sizes - creating hybrid sizes like 32D/DD or 32E/F.
On paper, it looked efficient: fewer SKUs, simpler inventory.
But the problem showed up fast.
Customers who’d worn their bras for years suddenly found that nothing fit the same.
That’s when I was called in to find out what had gone wrong.
The brand had kept their wire grade the same - 1.3 cm per cup size - even after merging two cups into one.
So their 32I/J wire, which should have measured around 37 cm, now measured closer to 31 cm - roughly equivalent to their old 32G.
The fit collapsed. Support disappeared.
Returns soared, and loyal customers felt alienated.
In the warehouse, the brand was left with mixed inventory and no clear way to identify which batches were correct.
Relabelling would have been expensive and messy. Replacing the stock even more so.
It was a costly lesson in how small grading errors multiply fast - especially in technically complex garments like bras.
Poor grading doesn’t just distort a measurement chart - it distorts your entire customer experience.
• Fit feels inconsistent.
• Comfort disappears.
• Trust erodes.
• Sales drop.
Your customer doesn’t know it’s a grading issue - they just know your brand’s sizing “feels off.”
And once that perception sticks, it’s hard to undo.
Grading is one of those areas where prevention really is better (and cheaper) than cure.
Think of it as your guiding light - a document that standardises how your brand grades every product, every time.
It should outline your core grade rules, including key measurements and their increments, so you can easily cross-check any spec the factory sends back.
When everyone’s working from the same playbook, it’s far easier to spot errors before they snowball.
If the grade looks uneven, ask why. There might be valid reasons (like a graded hook & eye width), but they should always be clearly explained.
Don’t treat each sample in isolation.
Fit multiple sizes side-by-side to see how proportions evolve. That’s where you’ll spot where a grade has gone off track.
If your team doesn’t have grading knowledge in-house, hire someone who does - even short term.
An experienced technical consultant can set up your grading system correctly, train your team, and save you from months of confusion and costly returns later.
Grading might not be the most exciting part of product development, but it’s one of the most powerful tools you have for consistency, comfort and customer trust.
It’s the bridge between your base pattern and your full size range - the quiet system that keeps your fit believable across every size.
So don’t leave it to chance, or to your factory.
Own your grade, document it, and understand it.
Because when your grading is right, everything else - from fit to loyalty - starts to fall into place.
