How to make any chair more ergonomic without buying a new one

You can make most chairs far more comfortable with things you already own. Roll a towel into the curve of your lower back, sit on a firm cushion if the seat is too low for the desk, put a box or a stack of books under your feet if they don't reach the floor, and lower, pad or ignore armrests that push your shoulders up.

Then change position often, because no chair, however well set up, is meant to be sat in without moving. These fixes work on office chairs that have lost their adjustments, dining chairs pressed into service at a home desk and the old chair in the spare room. Start by checking what your chair can already do, then work from your lower back down to your feet and back up to your arms.

First, check what your chair already does

Many office chairs have adjustments their owners never find. Before adding anything, sit in yours and feel under and around the seat. Depending on the chair, you may find:

• Seat height: usually a lever under the seat, often on the right.
• Tilt tension: a large knob under the front of the seat that sets how hard you have to push to lean back.
• Tilt lock: a lever that holds the backrest upright or lets it rock.
• Seat depth: a lever or handle that slides the seat forward or back.
• Back support: a backrest that slides up and down, or a lumbar pad or knob.
• Armrests: buttons that raise or lower them, and on some chairs a way to slide or swivel them.

Use whatever is there first. The fixes below fill the gaps a chair can't adjust for itself. If you want a full order for setting up the chair, desk and screen together, desk setup for a Mac walks through it.

Support your lower back with a rolled towel

This is the most useful single fix for most chairs. Your lower back has a natural inward curve. A flat or hard backrest leaves a gap behind it, and over the day you sink into that gap and slump.

1. Make the roll. Fold a hand towel in half lengthwise and roll it up firmly, to roughly the thickness of your forearm.
2. Place it. Sit all the way back and put the roll behind you, in the small of your back, at about belt height.
3. Lean back into it. It should fill the gap so you feel supported, not pushed forward. If it feels like it is shoving you, use a thinner roll or move it up or down a little.
4. Keep it there. A couple of rubber bands stop it unrolling. A strip of fabric or an old belt around the backrest holds it at the right height.

A small cushion or a folded sweater works the same way. If the seat is so deep that you can't sit back without its front edge pressing into the backs of your knees, put a firm cushion behind your whole back instead. It brings the backrest forward to meet you, so you can sit back without perching.

Raise the seat with a firm cushion

Dining chairs and many older chairs sit too low for a desk. Your keyboard ends up above your elbows and your shoulders lift to reach it. The goal is a seat high enough that your forearms are roughly level with the keys, as set out in ergonomic desk height.

• Use something firm. A firm cushion, a folded blanket or a couple of folded towels. A soft pillow squashes flat within an hour and you sink back down.
• Stop it sliding. A piece of non-slip shelf liner or a rubber mat under the cushion keeps it in place, and a cushion with ties can be fastened to the chair.
• Pad a hard seat while you're at it. The same cushion makes a wooden seat easier to sit on for long stretches.
• Check your thighs. Once you are higher, make sure your thighs still fit under the desk.

Make a footrest from a box

Raising the seat often leaves your feet off the floor. Feet that dangle press the front edge of the seat into the backs of your thighs, and most people respond by perching forward or tucking their feet under the chair. Neither lasts comfortably.

Anything firm and flat can be a footrest: a sturdy box, a ream or two of paper, a stack of books, a step stool or a yoga block. Make it:

• high enough that your feet rest flat and your thighs are roughly level,
• wide enough to shift your feet around on, and
• steady enough that it doesn't slide away when you push on it. A mat underneath helps on a smooth floor.

Some people like a slight slope, with the far edge a little higher. A thin book under the back of the box gives you that.

Deal with the armrests

Armrests can help or hurt, depending on where they sit.

• Too high. They push your elbows up, and your shoulders follow. Lower them if they adjust. If they don't, many unscrew from under the seat, or you can simply let your elbows hang by your sides and not use them.
• Hitting the desk. If they stop you pulling in close, you end up leaning forward to reach the keyboard. Lower them below the desk edge, take them off, or swap to a chair without them for desk work.
• Hard. Wrap a folded towel around them and hold it in place with a band or two.
• Too wide. If you have to hold your arms out to reach them, ignore them and let your arms hang.

Try not to lean on one armrest for hours. It tends to leave one shoulder higher than the other by the end of the day.

What about a dining chair or a stool?

A dining chair usually needs most of the fixes at once, because it has a hard seat, an upright back and a fixed height. Here they are in one place.

A stool or a bench has no backrest at all, so your own muscles hold you up the whole time. That is fine in shorter spells. Sit tall with your feet flat, and switch to a chair with a back for long stretches. A sofa or a bed is a different problem again, covered in working from the couch with a MacBook.

How often should you change position?

There is no magic number, and no chair removes the need to move. Even a well supported position starts to feel stiff when you hold it for hours, because the same muscles carry the same load the whole time. Shift often: lean back for a while, sit forward, cross and uncross your legs, stand up between tasks, walk to the window. A common rule of thumb is to get out of the chair at least once an hour.

Remembering to use what you built

The towel and the box are easy to forget once they are in place. By mid-afternoon you are perched on the front edge again, a hand's width away from the support you set up that morning. Notchpals, which turns the notch on your Mac into a home for reminder characters, has a Posture area for this. Matsu, an ancient bonsai with excellent advice, is one of its characters, and one of its posture checks is the towel roll's whole reason for existing:

MatsuBack against the chair. Even old trees lean on the hillside. It is allowed.

Its Shoulders down visit is a good moment to check the armrests too. If your elbows are propped high, that is often where raised shoulders come from:

MatsuLet your shoulders fall, like branches when the snow slides off.

Matsu asks you to adjust, not to freeze, and takes your Done on trust. Getting up is a separate job, and a Movement character in your crew handles it, asking you to stand after most of an unbroken hour at the Mac.

A better chair setup can make everyday aches less common, but it can't treat anything. Back pain that lasts or keeps returning, or numbness or tingling in your legs or feet, is a job for a doctor or a physiotherapist, not another rolled towel.