The right fit isn't one thing. A base layer needs to stay close; a shell needs room for everything underneath. Get either wrong and the clothing stops working.
Well-fitted outdoor clothing performs better. A close-fit base layer wicks because the fabric stays in contact with your skin. A correctly-sized shell holds its back coverage when you raise your arms. Trousers with the right hip measurement don't pull across the seat on a long descent. The difference is rarely obvious in a changing room, but it shows up quickly on the hill.
How to Take Your Measurements
All you need is a soft tape measure and about five minutes. Measure over the base layer you plan to wear underneath each garment, not bare skin. That small detail makes a real difference, particularly for mid layers and shells.
Chest
Wrap the tape around the fullest part of your chest, keeping your arms relaxed at your sides. Don't pull it tight and don't let it sag. Note the measurement at a natural breath out.
Waist
This is your natural waist, which sits above your hip bones and below your ribs. It is not your trouser waistband. Many people measure two inches too low and end up with shorts or trousers that are too long in the rise.
Hips
Measure around the widest part of your hips and backside. For trousers and tights, this is often the critical measurement, particularly if you have a different hip-to-waist ratio.
Inside Leg
Stand with your feet about 15cm apart. Measure from the floor up to your crotch. It helps to have someone else measure this one accurately. Take this measurement in the footwear you plan to wear, or allow a couple of centimetres if you will be wearing boots with thick soles.
Neck and Sleeve Length
Neck circumference is relevant for close-fitting base layers and some mid layers. Measure around the base of your neck where a collar would sit.
For sleeve length, measure from the centre back of your neck, out across the shoulder, and down to the wrist with your arm slightly bent. This is the measurement that varies most between brands, so it is worth checking if you have particularly long or short arms relative to your chest size.
How Fit Varies by Garment Type
The right fit isn't one thing. A base layer and a hardshell are designed to work differently, and understanding that changes how you read a size chart.
Base Layers
Base layers should skim the body. Not tight enough to restrict breathing, but close enough that the fabric stays in contact with your skin. If there's a gap between you and the fabric, moisture sits there instead of moving through it. You feel it first as dampness, then as cold.
Buy to your measurements. If you're between sizes, go to the size that matches your chest rather than down to the one that feels snugger. If you're running or moving at high output, fit matters even more — a base layer that works at walking pace can feel clammy and restrictive when you're generating real heat. The trail running base layer guide covers that end of the spectrum in more detail.
Mid Layers
Fleeces and insulated jackets need a relaxed fit — room to move your arms freely and space for a base layer underneath. But relaxed doesn't mean boxy. A fleece that hangs off your shoulders won't trap warmth effectively, and you'll feel it as cold air pooling around your torso rather than warmth building inside it.
The fit to aim for: comfortable across the chest and shoulders, not pulling at the back when you reach forward.
Hardshells and Softshells
This is where layering allowance becomes critical. A hardshell or softshell needs to go over a mid layer, so it needs room. The test: put on the mid layer you plan to wear underneath, then try the shell. Raise both arms straight above your head. The hem shouldn't lift more than an inch or two. If it pulls up significantly, you've lost the back coverage that keeps you warm and dry.
Check that the shoulders sit correctly too. If the shoulder seam drops down your arm, the jacket is too big and the hood will be misaligned in bad weather.
See our full layering guide for how the system fits together.
Trousers and Tights
Seat room and hem length are the two measurements that catch people out. You need enough room through the seat and thighs to squat, step up onto boulders, and crouch without the fabric pulling tight across the back. Trousers that feel fine standing in a shop will tell you everything on the first steep climb.
Hem length is best judged with boots on. Trousers that finish at your ankle in trainers will sit above the boot line in fell boots, which lets in weather and debris at exactly the moment you don't want it.
Gloves
Gloves should be snug but not cutting off circulation. Measure around the widest part of your hand, excluding your thumb. Your fingertips should reach comfortably to the end of each finger. Too much room and the glove bunches at the knuckles, which kills dexterity when you're trying to work a zip or a buckle in the cold. Too tight and your fingers go numb faster, which is the problem gloves are supposed to solve.
Technical Fit Terms Explained
You'll see terms like "articulated" or "anatomic cut" on technical outdoor clothing. They describe specific design choices that make a real difference in use.
Articulated elbows and knees: The fabric is pre-shaped so that the garment naturally follows the bend of your arm or leg. Without this, a straight-cut sleeve pulls tight every time you reach forward.
Drop hem: The back of the jacket is cut longer than the front. This keeps your lower back covered when you lean forward over handlebars, an ice axe, or a map.
Underarm gussets: A diamond or triangular panel of fabric stitched into the armpit. It allows full arm raises without the hem lifting or the side seams pulling. Essential for climbing, scrambling, and anything where your arms go above your head regularly.
Layering Allowance
Outer layers need room for inner layers. Most of our shells are designed with standard layering allowance built in, but if you run cold and habitually wear a thick fleece underneath, that allowance can be used up. In that case, size up one from your chest measurement.
For base layers, buy to your actual measurements. Sizing down doesn't help you wick more efficiently — it just restricts your movement, which matters most when you're working hard and generating heat. If you want a more activity-specific view of which combinations work together, the guides for trail running and hillwalking cover the full system.
Men's vs Women's Fit
Women's outdoor clothing is cut with a shorter body length, narrower shoulders, and more room through the hips. The patterns are designed around a different body proportion, not adapted from a men's template.
Unisex garments are designed to men's measurements. If you're a woman ordering a unisex piece, check body length and shoulder width in the size chart rather than going by chest alone. Body length catches people out most often: a unisex jacket sized for a 36" chest may have a torso length designed for a taller person, which means the hem sits lower and the pockets land in the wrong place.
Most of our clothing goes up to XXL or size 20 and above. For more on the range and how we think about sizing, the sizing matters piece has the full picture.
Between Sizes: How to Decide
It happens. Bodies don't follow size charts exactly, and outdoor clothing involves layering which adds another variable.
The general rule: go up for anything you're layering over other garments. Go to your measurements for base layers and close-fitting pieces. When you're caught between sizes on body length versus chest, prioritise body length for taller builds and chest for broader ones.
If you're still unsure, check the returns policy before you order. Getting fit right without trying something on is always an educated guess, and knowing you can exchange easily takes the pressure off getting it perfect first time. For footwear, the same logic applies — our walking boots guide covers foot measurement and fit in the same way.