Some years ago, the food advocate Michael Pollan, author of In Defense of Food: An Eater’s Manifesto, succinctly summed up the best advice he could offer on how a human should eat: “Eat food. Not too much. Mostly plants.” It’s so simple you’d hardly think it need be stated, and yet the global rise of obesity and diabetes, coupled with an overcrowded marketplace of fad diets, makes its necessity clear.

Like food, fashion is a global industry that people have no choice but to take part in, simply because clothes are a necessity. And as with food, many of us in the wealthy world are over-consuming fashion—draining natural resources, polluting rivers with dyes, stuffing our closets, and filling landfills with an unprecedented amount of unwanted clothing.

A formula much like Pollan’s could work equally well in for clothing, and it would go something like this: Buy better clothes. Buy less of them. Wear them more.

I’ve argued before that the next item of clothing you buy should be so expensive it hurts, as a personal safeguard against the casual overconsumption of clothes that has become a compulsion for many of us. It’s largely a reaction to the easy availability of cheap clothes, which offer a nearly narcotic buzz with their low price tags.

Here’s the thing: That price tag isn’t telling the whole story. Even a gorgeously tailored black dress isn’t worth much to you if you already have 10 just like it. A $15 t-shirt is no bargain if it’s worn out after a few washes. And those jeans on sale aren’t worth $40 if you’ll wear them just twice before consigning them to the back of your closet.

So here’s a thought experiment for the next time you shop: Think of your purchase as the beginning of a relationship with an item of clothing. It starts at the earliest stages of the supply chain, is carried on by the people who design the clothes and those that stitch them together, and ends in a landfill or recycling plant. You enter it at the point of purchase, and from that point on, that piece of clothing is your responsibility—it was created for you, and it’s yours to wear, to care for, and eventually to dispose of. You have to decide whether that relationship will be worth what it costs, in dollars and cents but also in terms of its environmental toll.

Here are three points to consider next time you go shopping. They can help you figure out the real “value” of what you’re buying, beyond the price printed on the tag. For most of us, buying nothing is not a realistic goal—but the next best thing you can do is buy better clothes, buy less of them, and wear them more.

So before you buy another piece of clothing, ask yourself these questions:

How much will I wear it?

There’s little hard research on how often people generally wear their clothes, but one survey of 2,000 women in the UK found respondents on average wore an item seven times. Other researchers have found that some women wear an item just once because they don’t want to repeat an outfit in a photo posted to social media. Overall, data from the US Bureau of Labor Statistics’ Consumer Price Index show, today’s cheaper clothes allow us to buy more while spending less of our income.

People often buy items on sale because they feel they’re getting a bargain. In fact, one study published last year in the Journal of Marketing Research found that looking at a product’s price first, before examining the product itself, led subjects to make price the primary factor in their purchase. But a cheap item isn’t always cost-effective in the long run.

One way to determine the “real” price is to consider a metric called “cost per wear” (CPW):

Total amount paid for the item / the number of times you wear it = CPW

As GQ has noted, the point is that an item you wear repeatedly over time can have a better value than something cheaper that you wear just a few times, or for a season. A $50 pair of jeans bought on impulse and worn just 10 times has a CPW of $5. Meanwhile, a $100 pair of jeans bought for the long haul and worn 50 times has a CPW of $2. The more expensive jeans are actually the better deal in dollars and cents.

Reuters/Mario Anzuoni On sale.

CPW also favors items that last longer. A $10 t-shirt that shrinks, pills, or fades to unwearability with a few washes has a higher CPW than a $60 t-shirt that can be worn regularly for a couple of years. Price doesn’t guarantee quality, but low cost doesn’t guarantee a bargain, either.

There are different ways to use this information when you think of buying something, but the point is to think strategically about purchases, rather than buy on impulse. One creative Reddit user set a goal of $1 per wear for his purchases. For him, a $50 pair of jeans would have to get at least 50 wears before they’re resold, recycled, donated, or discarded.

One caveat about cost per wear: Be honest with yourself in your assessment of how much you’ll wear something. Don’t let it become a justification for buying something, expensive or not, that you really won’t use.

How much do I already own?

The chief design officer at California Closets, a nationwide closet-design firm, told the Wall Street Journal (paywall) in 2013 that people in wealthy societies typically wear about 20% of their clothes on a regular basis.

If that sounds like you, try taking an inventory of your own closet to figure out what share of your clothes you actually wear, and what those items have in common. If all your brightly colored items are collecting dust while you wear black and grey every day, it may not be worthwhile to buy a new chartreuse blouse.

Designer Michael Kors has espoused what might be called the “meat and potatoes” rule: 70% of your wardrobe should be meat and potatoes, or the main items you return to over and over. Only 30% should be dessert: the sparkly top for going out, for instance, or those brightly colored pants that only match two of your shirts. “Too many women get the proportions the other way round, then can’t figure out why they can’t get dressed,” Kors has been quoted saying.

When you consider a purchase, ask yourself whether it’s meat and potatoes or dessert, and then whether it’s worth adding to your closet at all.

Here’s another percentage to consider to help put that question into perspective. Each piece of clothing you own is one share of your total wardrobe. So if you have 50 items of clothing, each one represents 2% of your wardrobe.

100 / number of items in your wardrobe = % of wardrobe

You’ll notice right away that the more stuff you have, the smaller the share each individual piece of clothing represents. Each new purchase shrinks that share a little more, and when you own a lot, it makes it harder to maximize the proportion of clothes that you wear regularly.

Because it favors a smaller wardrobe, this way of thinking can nudge you toward buying investment pieces rather than stocking up on cheap items. You may choose to buy one nicer pair of jeans for the cost of three cheaper pairs. The value of those nicer jeans will be higher in your small wardrobe, and it’s likely you’ll wear them more, improving their CPW and avoiding that 80/20 imbalance.

You’re also likely to be happier about your shopping. A study (pdf) in the Journal of Marketing Research in 2008 found that, in the long term, shoppers didn’t terribly regret splurges. What they often regretted was picking the cheaper version, or something that they thought would be more practical, instead of the item they really wanted. So, again, consider spending more per item, buying less overall, and focusing on the meat and potatoes rather than dessert.

(And if this exercise inspires you to clear out your closet, Marie Kondo has a method that can change your life.)

How long will it last?

The apparel industry is a massive producer of greenhouse gases. “Industry-wide, greenhouse gas emissions in one year are equivalent to driving to the sun and back more than 1,000 times,” says a report by MIT’s Materials Systems Laboratory (pdf). On average, one t-shirt has the climate impact of driving a passenger car five miles, it noted.

A garment’s carbon footprint doesn’t just come from making it. Washing it, and especially drying in a dryer, uses a lot of energy over time.

Still, that footprint decreases with the garment’s longevity. The Carbon Trust, a coalition of organizations focused on reducing emissions, did an analysis (pdf) of carbon emissions per year from 50 wash-and-wear cycles for a t-shirt, factoring in whether the t-shirt would need to be replaced after a certain number of wears. If a t-shirt lasts for 25 wash-and-wear cycles, for instance, it would take two of them to hit 50 total wears.

The group estimates that a typical t-shirt sold today is responsible for about 15 kg CO2 over its lifetime, about half of which comes from washing and drying it. But the longer it lasts without being replaced, the smaller its footprint becomes.

When you think of the next item you want to buy, it’s a better value again to go with the item that will last the longest. Often that isn’t the cheapest one. High-quality cotton, which tends to have a longer staple length, making it softer and stronger, costs more. Organic cotton has a smaller starting footprint than conventional cotton, too, and is again pricier.

Again, a higher price tag doesn’t guarantee a sturdier product. But something cheap that isn’t built to last can have a much greater cost to the environment. (It’s also worth noting that very cheap items are often made by shortchanging workers.)

This argument runs directly counter to the culture of fast fashion, which thrives on short-lived trends, so clothes don’t need to last. Instead of accepting that premise, try to choose well-made items that you think you’ll want to wear season after season. And to extend the life of your clothes, avoid the dryer when possible, not just because of the energy it uses but also because it’s drying, not washing, that’s most responsible for warping them.

Wash in cold water to further reduce the impact, wash clothes only when they actually need cleaning, and if a piece of clothing is stained or damaged, consider repairing it rather than replacing it.

“As individual consumers, the single best thing we can do for the planet is to keep our stuff in use longer,” Rose Marcario, Patagonia’s CEO, wrote in a company blog post. “Fixing something we might otherwise throw away is almost inconceivable to many in the heyday of fast fashion and rapidly advancing technology, but the impact is enormous.”

Make it count

These different types of value don’t necessarily mean you should buy the most expensive item you find, or that you should cease shopping altogether. There are always worthy exceptions. Items for formal occasions, or the glamorous or spangly “dessert” in Kors’ formulation, don’t get as much wear but they still serve important functions. And if there’s something you love or attach sentimental value to, but won’t wear as often as a go-to t-shirt, that’s perfectly alright.

The point is simply to suggest that it’s less “costly”—to yourself and to the world—to buy one item that you’re going to wear frequently, whether it’s a t-shirt, a coat, or a blazer, than several you’ll use sparingly.

So next time you think of buying a new piece of clothing, take a moment to consider how much you’ll wear it, how much you already own, and how long you think it will last. It may give you a new perspective on the price tag.