Why does Magic Fit® need my birthday? Why does Magic Fit® need my birthday?

Why does Magic Fit® need my birthday?

Glad you asked because this question has two interpretations. 

The first is asking why we need someone’s age for Magic Fit®, and the second is asking why we need your date of birth, when surely year is enough.


Why do we ask for age? 

Intuitively it might feel like age doesn’t play a part in predicting measurements, because after all, the length of your arms hasn’t changed since the day you stopped growing.

And you’re right. Age is not statistically significant when trying to predict arm length. However, age is statistically significant for predicting waist, hips and bicep based on our analysis of biometric data collected from over 8000 individuals, which we overlaid with data manually captured from thousands of in-store fittings to test the validity of the algorithm that would become Magic Fit®.

Age is statistically significant for predicting waist and bicep measurements, among others. 

What we achieved with Magic Fit® is novel, but not new as research into body composition dates back decades. We're standing on the shoulders of giants such as Pollock who found bra and cup size to be statistically significant when calculating body density for women in the 1970s.


Our body shapes change with age


Then in 1989 Shimokata studied 1179 men and women and was able to identify a trend showing increase in upper and central body fat deposition with age. Followed by Deurenberg in 1991 who studied 1229 men and women and was able to predict body density and body fat percentage using height, weight and age as independent variables. Both Shimotaka and Deurenberg each created prediction formulas not dissimilar to Magic Fit®.


Custom fit to your body with magic mathematics.


So, age - along with height and weight (and bra for women) - allows us to build an accurate statistical model which is the core of Magic Fit®. But a statistical model is only ever predictive and cannot account for the individuality of every body, so it’s important to remember this is only the first of four layers in Magic Fit® and these measurements alone do not define you. 

We know that some people were on the swim team and others carry their weight in their tummy or maybe their thighs. We also know that some people have disabilities which affect body shape (sometimes significantly). 

You tell us what makes you special, and we make your Tee on-demand to fit you (and only you) - with every Tee backed by our perfect fit guarantee.

Nature and nurture need to be taken into account, so we added Natural Language Processing (NLP) to account for individuali-Tee. You tell us what makes you special, and we make a Tee on demand, to fit you and only you - with every Tee backed by our perfect fit guarantee. Yes, really.  


Why birthday then, and not just age?

At Citizen Wolf we’ve grown up really close to our customers. Our roots are in physical retail and to this day our factory is still a shop so we’ve always had a high touch experience. 

We’ve gotten to know many, many customers over the years and some of them have become our closest friends. We didn’t want to let go of that friendly, personalised feel just because we started selling online. It’s why we pride ourselves on delivering the best customer service; because that’s what we would do for our friends.

Friends also celebrate birthdays, so when you share yours with us we get the opportunity to surprise you on your special day 😊

As always, if you have any questions, opinions, praise or criticisms... just howl!



PS - Your data is only ever used to make the best fitting Tees in the universe and is held securely with the same online encryption used by your bank. If you’re still uncomfortable just use January 1 with the correct year.



Prediction of body density in young and middle-aged women. Journal of Applied Physiology 1975 38:4, Pages 745-749 M. L. Pollock, E. E. Laughridge, B. Coleman, A. C. Linnerud, and A. Jackson

Studies in the Distribution of Body Fat: I. Effects of Age, Sex, and Obesity. Journal of Gerontology, Volume 44, Issue 2, March 1989, Pages M66–M73 Hiroshi Shimokata, Jordan D. Tobin, Denis C. Muller, Dariush Elahi, Patricia J. Coon, Reubin Andres.

Body mass index as a measure of body fatness: Age- and sex-specific prediction formulas. British Journal of Nutrition, 65(2), Pages 105-114 doi:10.1079/BJN19910073 Deurenberg, P., Weststrate, J., & Seidell, J. (1991).


Written by Rahul Mooray