For those who are already familiar with how jeans are measured before shopping for denim.

Here are 4 key principles and some common sense that will help as you travel deeper into the world of jeans & selvedge denim.

• Universal rules in jeans sizing
• Size difference between sanforized denim and unsanforized denim jeans
• Unwashed jeans vs one washed jeans
• What you should never with jeans

Some Universal Rules in Jeans Sizing

(If you’re shopping for Japanese raw denim, skip ahead to point 3.)

Vanity Sizing / Universal Sizes for Major Brands.

Most major brands try to keep an universal or generally consistent size across all jeans models.

For example, if you wear a W29 in major American brands, you’re likely also a W29 in Levi’s 501 or Uniqlo Straight Fit Jeans.

Even among smaller but well-known premium brands like Nudie Jeans, sizing generally aligns with these larger brands — usually a W29 in Levis is W29 in Nudie.

There can still be 1-2 size differences in different designs, and of course there will. Most brands will note this in their product descriptions or size recommendations.

Fit Variation Between Styles

In many cases, wider fits tend to run slightly larger at the waist compared to slimmer fits — often about one size difference.

For example,
I’m a W29 in Levis 501, the classic regular straight fit.
But I’m a W30 in Levis 511, the slim straight fit.

This happens because different fits are built from different pattern blocks and body shape assumptions. Naturally, the overall grading and silhouette vary from one fit to another.

Japanese Heritage Brands Have Their Own Sizing Logic

In general, Japanese heritage jeans fit about 1–2 sizes smaller than major American or global brands.

For reference,
I’m 170cm 60-65kg / about 6’8” 135-145lbs with a small tummy.
I wear W29 in Levis, Uniqlo and other major brands.

I wear W30 in ONI Denim.
I wear W31 in Momotaro.
I wear W31 in Pure Blue Japan.
I wear W32 in Resolute jeans.
Depending on the fit, I wear W29~31 in Full Count.

Because of this, you should generally go up at least one size from your usual when buying your first pair of Japanese jeans.
And most importantly — always check the size chart before you checkout.

Sanforized vs Unsanforized.

Before anything else, you’ll need to check whether the jeans are sanforized or unsanforized.

There’s a noticeable difference in both look and feel between selvedge sanforized denim and selvedge unsanforized denim, so let’s break it down.

Let’s break it down for you.

What is sanforized denim?

Sanforized denim is fabric that has been pre-shrunk. Jeans made from sanforized denim typically have minimal shrinkage — about 2–3%, though this can vary depending on the fabric.
The sanforization process involves treating the denim with steam, heat, and pressure to minimize shrinkage after purchase.
Most mass-produced jeans on the market use sanforized denim because it removes the uncertainty of how much a pair will shrink after the first wash.
Before sanforization was invented, all jeans were sold as “shrink-to-fit.” Levi’s still keeps this tradition alive today with their STF (Shrink-To-Fit) product line.

Key Features of Sanforized Denim

• Minimal shrinkage
• Easier to cut and sew
• More uniform appearance
• Softer and smoother on the inside

Advantages of Sanforized Jeans

• Feels more modern and refined
• Can appear more luxurious
• Offers a consistent fit across different fabrics
• Fits clean and straight
• Won’t loosen as much as unsanforized jeans
• Easier to find — most brands use sanforized denim
• Fades with sharper contrast
• Usually lighter in weight

What is unsanforized denim?

Unsanforized denim is raw denim that hasn’t been pre-shrunk at the mill. It skips any finishing process after weaving, which is why it’s also called “loomstate denim.”
This type of denim can shrink up to 10–20% after the first wash.

Key Features of Unsanforized Denim

• Significant shrinkage after the first wash
• Rougher texture
• Hairier surface

Advantages of Unsanforized Jeans

• Feels like wearing true vintage jeans
• Looks rugged and authentic
• Legs may twist after washing (known as leg twist)
• Unique hand feel that no other fabric can replicate
• Starts out rigid but softens nicely with wear
• Usually heavier in weight
• Fades with deeper, richer color and character depending on the weave

Why Japanese Brands Love to Use Unsanforized Denim

Most Japanese heritage brands tend to use only unsanforized selvedge denim.
The upside of this is to preserve the original, rough, untreated texture of selvedge denim.

You may have heard that some Japanese brands like to do things the hard way — and that’s true here.
The downside of using unsanforized denim directly is that pattern making and sizing become extremely challenging.
Each unsanforized fabric can shrink anywhere from 10% to 20%. This means the designer has to redraw and adjust the pattern from scratch to achieve the desired fit.

Imagine working with a fabric that might randomly shrink by 10% to 20%.
You probably need to make three times more samples than with a fabric that doesn’t shrink.

Because of this, unsanforized raw jeans are nearly impossible to standardize without spending an unreasonable amount of sampling cost.
Even with careful adjustment, most small manufacturers still struggle to achieve the perfectly "controlled" sizing.

As a consumer, your main goal is simple — get the right size.
That’s why checking each brand’s individual size chart is essential.

You’ll end up finding that Japanese jeans to fit 112 sizes smaller, sometimes even 3 sizes smaller, compared to US brands.

Sounds complicated?
Don’t worry.
Check out the next and final section to learn why you don’t actually need to stress about it anymore.

One-Wash Jeans vs Unwashed Jeans

To avoid the trouble of jeans changing in size or shrinking to a too small size that you can’t wear after the purchase and home wash.

Most raw denim brands today offer one of two options: jeans made from sanforized denim, or one-wash (rinsed) jeans made from unsanforized denim.

The goal is simple — remove shrinkage so you can wear them right away.

Here are all types of product combinations:

Sanforized Denim Jeans

• Unwashed: Shrinks only about 2–3% after the first wash.

• One-Wash / Rinsed: Lightly rinsed to remove shrinkage with minimal indigo loss.

• Washed: Fully washed to remove excess indigo and starch. The denim becomes softer and feels like a pair of broken-in jeans.

Unsanforized Denim Jeans

• Unwashed: Shrinks up to 10% or more after the first wash.

• One-Wash / Rinsed: Lightly rinsed to remove shrinkage while keeping most of the indigo intact. Some Japanese brands describe these as “washed,” but they actually mean rinsed or one-wash.

• Washed: Rarely done, since unsanforized jeans are meant to be worn raw. It’s uncommon for this type to go through a wash process.

What are pre-washed jeans?

All jeans start as raw jeans.
Pre-washed jeans are raw jeans treated in industrial laundry facilities with various washing and finishing processes that soften the fabric and give it a “lived-in” or vintage-faded look.

If you prefer to save the trouble to fade your own raw jeans, pre-washed jeans are one good option. They are also the most common type of jeans out there in the wild today.

We had the privilege of visiting one of the best denim laundries in Japan.
👉 Check out how a pair of pre-washed jeans are made with our trip to SAAB, Japan.(To be updated)

What You Should Never Do to Your Jeans — Especially Raw Denim

To keep your jeans in good condition.
Avoid doing these things to your beloved jeans:

• Washing with warm or hot water: Hot water will shrink the fabric — similar to the sanforization process — and may cause your jeans to tighten. In most cases, it will shrink to a baby size.
• Tumble drying: Due to denim’s structure, tumble drying will physically shrink your jeans, sometimes drastically.
• Always dry cleaning: Dry cleaning doesn’t fully remove dirt or particles trapped in the fabric. It’s best to wash your jeans occasionally with cold water instead.
• Using bleach: Bleach is denim’s worst enemy — it kills bacteria but also destroys color.
• Using too much detergent: A moderate amount like washing your other clothing is enough. Too much detergent can cause excess indigo loss and lighten your jeans.

You also shouldn’t worry too much about whether you should wash your jeans out of hygiene reasons.
An Autralian colleague student has done a research for us — the amount of bateria on a pair of jeans worn 2 week basically is the same compare to a pair of jeans worn 2 years.
So, whether to wash your jeans or not all come down to personal choice.
Read our jeans and stuff care guide for more info.

The same principles apply to most premium garments.

Wear and care is key to a beautifully aged piece of clothing.

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If you want to see how some of the world’s best selvedge denim is made,
👉 follow our visit to Kuroki Mill, Japan.(To be updated)