Twenty pieces. That’s it. Twenty is the magic number that makes up what Annmarie O’Connor, author of The Happy Closet, calls a You-niform. The 20 items break down as follows: one coat, three jackets, five bottoms, five tops, one dress, five shoes. Close your eyes and picture it: a lean, calm, minimal wardrobe. An inch of bare rail between matching wooden hangers, just like in the fancy shops.

A pared-to-the-bone wardrobe is the chicest kind. A wardrobe formula attributed to Coco Chanel has a staccato, telegram quality, like a string of her famous pearls: “Black and white. Good shoes. Dresses. Polish. Simplicity. Well-fitting clothes.” I have a soft spot for Cher Horowitz’s closet in Clueless, so vast it requires a computerised inventory, but my heart belongs to Joan Didion, and the packing list she kept taped inside a cupboard “which enabled me to pack, without thinking, for any piece I was likely to do”, she wrote in 1979.

The clothes on Didion’s list were: two skirts, two jerseys or leotards, one pullover sweater, two pairs of shoes, stockings, bra, nightgown, robe, slippers. Twelve pieces. Thirteen, if you include the mohair throw she wore for flights. “Notice the deliberate anonymity of costume: in a skirt, a leotard and stockings, I could pass on either side of the culture,” wrote Didion of her list. A 20-piece wardrobe has no room for site- or moment-specific fashion. No picnic dresses, no Christmas jumpers.

Ruthless, yes, but that’s the whole point. The minimal wardrobe is chic precisely because it speaks to laser-sharp focus. To pinpoint one number that works for all is the style equivalent of solving simultaneous equations. The person working in an office with a formal dress code has different wardrobe needs to someone who works from home. If you live alone, owning just one white shirt presents a challenge because if you are only doing one white wash a week when you launder your sheets, you are likely to need two shirts. And if you live with a jammy-fingered toddler, having just one white shirt would surely add to, rather than reduce, the stress of family breakfasts before work. Each of us has different variables – but in the end, we all want life simplified.

Stylist and personal shopper Colomba Giacomini tells clients who want to edit their wardrobes to pack an imaginary suitcase with the clothes they want to wear for the next fortnight of their life. The point of the exercise is to concentrate on the clothes that work for you now, and shake off nostalgia. “It might be a beautiful dress, but if you never wear it any more and you’ve got a great photo of yourself in it, you only need to keep the photo, not the dress,” she says. This approach will stop you falling for the “sunk-cost fallacy”, whereby we hold on to expensive clothes even if they don’t work for us. “If you spent a small fortune on clothes you didn’t wear, forgive yourself,” says O’Connor. “To clear out your closet, you need to clear out the self-criticism first.”

Photographer, model and Vogue contributing editor Laura Bailey once posted on Instagram a packing list for Paris fashion week that has stuck in my mind ever since. “Swim, Run, Shoot, Write” it began. So much more intelligent to select a wardrobe that can be mapped to how you spend your time – what O’Connor calls “the beats of your life” – rather than collecting a pile of pretty clothes. “I am on a constant mission to reduce my wardrobe,” says Bailey. “I aspire to a pared-down, curated life, although I’m nowhere near. I feel panicked by excess, exhilarated by giving things away.” Aiming to make your wardrobe smaller rather than to add to it is a win for sustainability – although only if it is sustainable. Having met clients who cheerfully throw almost everything out only to wake the next day panicked by their empty wardrobe and itching to go shopping, O’Connor advises that a major edit is best done in baby steps.

Everyone I speak to agrees you need just one coat – but not on what it should be. O’Connor recommends a trenchcoat; Giacomini “a generously sized overcoat with slight military detailing”; Bailey is loyal to a Bella Freud long, belted, houndstooth coat “that works for hikes with the dogs and for nights out”. O’Connor breaks her recommendation of three jackets down into “a blazer, a gilet and a collarless tweed jacket – that Chanel-ish kind that you often see in Mango and Zara”.

There is consensus that the blazer should be black, single-breasted, sleek enough to work for day or evening. Wardrobe NYC, created by designer Josh Goot in partnership with Vogue Australia editor-in-chief Christine Centenera, elevates the curated wardrobe to its most chic iteration, with seasonal mini collections which are sold as standalone capsule closets. The hero piece of Wardrobe NYC’s permanent collection of classics – to wear with the perfect white shirt, the most flattering black leggings – is a black blazer. Giacomini concurs: “A beautiful black blazer can do day or night.”

Five bottoms can be broken down, says O’Connor, into “one skirt, two pairs of trousers, one pair of jeans and one pair of khakis”. She advises choosing trousers that can span “business-casual” and weekend. My tip – a pair that will see me through a fashion week in Milan or Paris – is a dark, straight-leg trouser with belt loops, in a relaxed fit, so that they can slouch a little on my hips or be belted for a more formal look. Giacomini can’t whittle jeans down to one pair, insisting on at least two: “one straight leg blue jean – the classic – but also a darker, floor-length pair with a slight bootcut, to wear with heels”. None of O’Connor’s recommended five shoes are a traditional high heel. She recommends ballet flats, slingback kitten heels, loafers, white sneakers and a lace-up ankle boot.

Colour is to be applied sparingly. Navy and grey are welcome, “but you don’t want to open your wardrobe and have it look like a unicorn’s hen party”, counsels O’Connor. Yet even the most streamlined wardrobe must allow room for a little freedom, a get-out-of-jail-free card. O’Connor allows for two “freebie” items – favourite accessories, perhaps. Laura Bailey keeps a beloved clothes rail in her studio “of just a few things I need – favourite knits and an old raincoat and dungarees for shooting in all weather. It combines the practical and the fantasy. I love that rail, because it makes me feel free – like anything’s possible.” Giacomini still buys magical pieces that catch her eye, “But only things that I really, truly love,” she says. “I ask myself: am I going to be obsessed with this in three years’ time?”

Most of us are deeply irrational, or at least conflicted, about the notion of choice. We might be happy to have the same breakfast every day, yet balk at the idea of having the same dinner three nights in a row. We can be seduced by the mental space freed up by owning just a few choice pieces of clothing, and then find ourselves in mourning for an eclectic wardrobe that catered to a spectrum of moods. To make your peace with a minimal wardrobe requires you to embrace simplicity as a positive and chic choice in itself. “There is a resolve that goes with having a minimal and beautifully made wardrobe” says Goot. “There is a relief and an ease to it that feels really positive. It enhances your lifestyle, rather than detracting from it.”

Instead of defining your style anew every morning by putting together an outfit, you are making a bold, enduring fashion statement. “The point isn’t to be abstemious for the sake of it,” says O’Connor. Less stuff equals more ease. Fewer clothes add up to more happiness. If there is such a thing as a one‑size-fits-all wardrobe, 20 pieces could be the answer. But you do the maths.