T-Shirts Unravelled

January 6, 2016 | Comments

We washed, dried, measured and weighed 800 of the most popular men's t-shirts available online. The shirts included a wide variety of price points ($5-$50), sizes (XXS up to 6XL) and fits ("slim", "tall", "relaxed", etc.). After compiling the data, we worked with beta testers in NYC to develop an algorithm that could recommend t-shirt brands and sizes for a wide range of body types. We're still tweaking the math on that algorithm, but in the meantime, we thought we'd share some of the data that has surfaced from our project so far.

T-Shirts Widen and Shorten Over Time

T-Shirts change in consistent ways over time. Each time a t-shirt is washed, it shrinks, and each time it is worn, it expands. The expansion in the chest is almost 2x more than the expansion in the length and most of that expansion happens in the first two hours of wear.

What surprised us was that over the course of many wash cycles, the chest and waist will drift wider and the length will drift shorter. The chart below shows the evolution of 10 different t-shirts over 16 washes, averaged to one line. (We calibrate our search results to the dotted lines shown below).

A Zara XL is like a J. Crew Medium

No two brands have the same sizing system, and the differences between them can be vast. The chart below provides a breakdown of chest measurements for sizes Small, Medium, Large and XL. The chest is measured as the distance between the shirt's arm seams.

Expressed as chest x length, the average Small is 19.0" x 26.3", the average Medium is 20.5" x 27.1", the average Large is 22.0" x 27.8", the average XL is 23.5" x 28.6". The length breakdown is provided below.

Fabric Weight and Price Have No Relationship

One of our assumptions going into the project was that cheaper t-shirts would weigh less (per square yard). In fact, heavier t-shirts were less expensive, on average, than lighter ones (overall the correlation is very weak). Commodity cotton is cheap right now (only $0.70/lb), so raw materials comprise only a tiny portion of a manufacturer's cost structure.

The culprit is manufacturing variance

You may have had this experience before: You buy two identical articles of clothing. They are the same brand, style and size -- maybe even the same color. They are exactly the same except that one fits, and the other does not. The problem is manufacturing variance.

To test manufacturing variance, we measured 20 identical new t-shirts. These shirts were priced in the $20 range. The graph below depicts the distribution in chest width and length, which each have a standard deviation of about one fifth of an inch.

It's probably more helpful to think about the size of a particular of shirt as a distribution, rather than an exact number. Maximize your chance of success as a consumer by buying t-shirts where the average produced is a very good fit. This way only extreme outliers won't fit you very well.

It's the dryer, not the washer, that shrinks t-shirts

One thing you hear everywhere is that washing clothes in hot water will cause them to shrink. While hot water may cause shrinkage in wool garments, for cotton and polyester t-shirts, the washer settings don't make a big difference. The biggest determinant of shrinkage is whether the shirt went in the dryer or not. (We wash and dry all t-shirts using a warm wash and normal/warm dry cycle).