Cost per wear - or evaluating the relative cost of an item by how often we wear it - has been an established fashion tool for a long long time. I myself have been using it for over three years now, not only for estimating how often I may wear an item before deciding to buy it, but also for actually tracking how often I wear things. Whilst I admit it requires a certain level of organization [and geekiness: hello Excel chart almost every day], it has been a very interesting and helpful experiment which I have no intention of giving up and which I whole-heartedly recommend to all.
Let me share some lessons it has taught me:
1 - Items that I feel I have worn 'a lot' may not actually be getting that much wear at all. It is rare that we will wear an item [save coats, jeans, cardis and accessories] more than once a week due to laundering/thirst for novelty/etc -- which, if you think about it properly, means that in a country with 4 seasons [=roughly 13 weeks per season], even if spring and autumn have similar weather, it is rare for such a piece to be worn more than 15-25 times a year - and this is for items you wear every week of a season, which will feel like 'a lot'! Doesn't this seem like very little, in fact? For really seasonal items [really hot/really cold weather, unless you live in a climate where this is normal], the number will be even lower. A good reason to re-think how much we spend on obvious trends that cannot be worn for several years.
2 - The items that one can wear day in, day out [coats, blazers, jeans, scarves, shoes, bags, accessories] really are the most important purchases. Yes, I know you read this everywhere, but it does make a difference to actually see your own, personal, black and white proof for it! These are the items that you have the potential to wear 100+ times. This doesn't mean these pieces are always worth spending a fortune on, but that they need to be chosen very carefully, and that if they are chosen well, they are indeed worth spending more on as they truly will be worn a lot. Example: it took me a long time last winter to fork out an amount for a winter scarf that I felt was too high for such a simple accessory [although it would have been normal to pay for, say, a jumper], but not only have I worn it a whopping 147 times since but every single time I do, I am delighted to have bought it - it is a smart, stylish, quality piece that single-handedly manages to make me look sophisticated while out and about [at least so I think ;)].
3 - Items for 'special occasions' [whether this be a fancy evening or a beach holiday that you only go on once every few years - anything that counts as irregular for your lifestyle] are only worth the money if they are classic and quality enough to last until the next time they may be needed. If you are unsure about whether you will have other occasions to wear such an item to, or whether it will still suit your style or figure for years to come, maybe it's best if you borrow/rent one, or make sure you can re-sell it after the event. [I do not recommend going for a super cheap option - for one, noone wants to look cheap; secondly, it still means you will be chucking it away after very little wear: not cool.]
4 - When I notice I haven't worn something much, I make a conscious effort to try to find ways of wearing it. Yes, there is a definite motivating factor there; the tracking system highlights which pieces do not get much attention and encourages reaching for more than just your favourite items, thereby enhancing creativity and offering the chance to surprise yourself regularly [with both your own creativity and the possibilities you discover].
5 - There are obvious patterns for which items I do not end up wearing much -- a great tool to use for avoiding future such purchases. Yes, there are items that however much I try to incorporate in a more regular rotation, still end up unloved. Upon closer inspection of these, there are always obvious explanations [they are in strong colours; too fitted; require hand-washing; etc.], which certainly spring to mind the next time I am contemplating purchasing something in the same vein. Money [well] saved!
6 - Conversely, seeing what you wear the most, and analysing what it is that makes you reach for these will offer helpful guidance for making future shopping choices. It is really helpful to be aware of your 'top items' - not just what you love but what you actually wear. What is it that you like about wearing them? Is it that they are comfortable? Elegant? Powerful? Fun? Whatever you come up with, these are most likely your key style words - use them consciously when out shopping to choose the right items and to build a wardrobe you will wear a lot.
7 - Seeing the actual number for how many wears an item lasts for is often an eye-opener. I have had shoes that only lasted for about 20 wears - for shoes, that is a very low number and their short life span may not have been this obvious had I not actually documented the number of wears. Lesson learnt regarding the brand.
8 - Finally, knowing the actual cost per wear for your items gives a good idea of how much they are worth paying for. Everyone will have their own limits - I for one do not feel comfortable if a regular item costs more than £10 per wear over a year, and tend to aim to go under £1 per wear for its full life cycle. This means £100 may be OK to pay for a pair of jeans but that for a dressy top that may not get that much wear, a £50 price tag may be the upper limit. Actual numbers help put things into perspective.
Overall, not only is it very interesting to track what you wear but also very useful, and hugely helpful for more conscious dressing and shopping and for a more mindful wardrobe. Simple but effective.
[As to how to do it? However you want. All you need to document is when you bought an item, how much it cost, and then mark each time you wear it. To add some extra flourish, you can also make a note of what you combined it with, very useful for when you are stuck for ideas. But beware - once you start with this, the sky is the limit of what else you can keep track of ;).]