You carefully wash your favorite blue jeans¹ in cold water, hoping to keep them the perfect size. But you still worry—could the detergent you're using be secretly shrinking them?

No, detergent itself does not make blue jeans shrink in cold water. Any minor shrinkage you might see is caused by the water relaxing the cotton fibers² and the washing machine's agitation, not the soap.

This is a common question, and it comes from a misunderstanding of what causes denim to change shape. In my two decades of manufacturing jeans, I've learned that fabric behavior is a science.

Detergent is designed to attract and remove dirt and oils; it doesn't have the chemical properties to alter and contract cotton fibers, especially without heat.

When a designer like Dean specifies a washing instruction for a garment, it's always about temperature and mechanical action, never about the brand of soap. The real culprits behind shrinkage are much more physical.

Will jeans shrink in cold wash?

You've always been told that washing jeans in cold water is the safest way to prevent shrinkage. But you're still not sure if it eliminates the risk completely.

Yes, jeans can shrink slightly in a cold wash, but usually only by 1-3%. This happens mostly with raw, unwashed denim as the cotton fibers relax in the water for the first time.

When we make jeans at the factory, the denim fabric is under constant tension. It's stretched on rolls, pulled through machines, and sewn tightly.

Raw denim—jeans that have never been washed—still holds all this tension. The very first time it gets wet, even in cold water, the cotton fibers finally relax and settle into their natural state, which causes a small amount of shrinkage.

Most jeans you buy today are "pre-shrunk" or "sanforized," meaning we've already put them through a washing process to get this initial shrinkage out of the way. For these jeans, a cold wash will produce almost no noticeable change in size.

Jean Type	Shrinkage in Cold Water	Why?
Raw Denim	1-3% (Slight)	Fibers are relaxing for the first time.
Pre-Shrunk	< 1% (Negligible)	The initial shrinkage was already removed at the factory.
Stretch Denim	< 1% (Negligible)	Elastane fibers help the jeans hold their shape.

Can you make jeans smaller by washing?

Your jeans have stretched out after a few wears and now feel a bit loose. You are hoping a quick wash will bring them back to their original, snug fit.

Yes, you can make jeans feel smaller by washing, especially if you use a hot dryer. The heat causes the cotton fibers to contract, but this is often a temporary effect that loosens up with wear.

This "fresh from the dryer" tightness is something everyone knows.

Heat and the tumbling motion of a dryer are what really make denim fibers contract and the weave tighten up. This is very effective for getting your jeans back to their original shape after they've stretched out from a day of wear.

For stretch denim³, the heat helps the elastane (spandex) fibers snap back into place. For 100% cotton jeans, the effect is real, but it won't last forever.

As you move around, your body heat and movement will slowly stretch the cotton fibers back out again.

So while washing and drying can make your jeans temporarily smaller, it's not a permanent solution for jeans that are a full size too big. For a permanent size change, you really need a tailor.

Does cold water help with shrinkage?

You're committed to keeping your jeans exactly as they are. You need to know if using cold water is truly the best defense against them getting smaller.

Absolutely. Using cold water is the single most effective thing you can do to prevent your jeans from shrinking. Heat is the main ingredient for shrinkage, and cold water removes it from the equation.

Heat gives the cotton fibers the energy they need to contract and tighten.

Cold water, on the other hand, is gentle. It allows the detergent to clean the fabric without triggering that aggressive shrinking reaction. So, washing on a cold cycle is step one.

Step two is just as important: air drying. The high heat of a machine dryer is the number one cause of significant shrinkage.

By washing your jeans in cold water and then hanging them to dry (or laying them flat), you are creating the safest possible environment for them.

This cold wash, air dry method is the universal instruction we provide to brands who want their customers' jeans to maintain their intended fit for as long as possible. It not only preserves the size but also protects the color and lifespan of the denim.

What temperature will shrink jeans?

You've decided you actually want to shrink a pair of jeans that are too big. You need to know what temperature to use to get the job done right.

To intentionally shrink jeans, you need to use hot water, ideally at 60°C (140°F) or hotter. For maximum effect, follow the hot wash with a cycle on the highest heat setting in your dryer.

Heat is the key, and the hotter, the better. A simple warm wash won't do much. You need to use the hottest setting available on your washing machine.

This intense heat, combined with the agitation of the wash cycle, will cause the cotton fibers to contract as much as possible.

Then, moving them directly into a hot dryer continues the process. The tumbling action helps tighten the fabric's weave even further.

Be aware that this process works best on 100% cotton denim. You can expect the most shrinkage in the length (inseam) and slightly less in the width (waist).

Keep in mind that this is a bit of a gamble—you can't precisely control the outcome, and there's always a risk of shrinking them too much.

Water Temperature	Expected Shrinkage	Best For
Cold (Below 30°C / 86°F)	Minimal to none	Preserving the original size and color.
Warm (40°C / 104°F)	Minor (less than half a size)	Everyday cleaning with very low risk.
Hot (60°C+ / 140°F+)	Significant (up to a full size)	Intentionally shrinking jeans that are too big.

Conclusion

Detergent does not shrink jeans in cold water. Shrinkage is a result of heat, water, and agitation, giving you the power to either prevent it with a cold wash or cause it with heat.

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