How to size hiking shoes so you get zero blisters

To size hiking shoes correctly, you should usually buy a pair half a size to one full size larger than your casual footwear. You need a finger’s width of space (roughly 1cm to 1.5cm) between your longest toe and the front of the shoe to prevent toe injuries when walking downhill.

I learned the hard way that my standard shoe size doesn’t work on a mountain. After a long day in the Peaks, I ended up with two black toenails because my toes kept bashing the front of my boots on every descent. It was painful and completely avoidable. When you figure out how to size hiking shoes, you have to account for things your office shoes never deal with, like gravity and swelling.

Measure your feet in the afternoon

Your feet aren’t the same size all day. As you walk, blood flow increases and your feet naturally expand. If you try on shoes at 10:00 AM, they might feel perfect, but by 3:00 PM on a trail, they will feel like torture devices. I always wait until later in the day to go boot shopping or do my measuring. This mimics the “swollen” state your feet will be in after five miles of hiking.

The insole test

This is my favourite quick trick. Most hiking shoes from brands like Merrell or Scarpa have removable insoles. Take the insole out, place it on the floor, and stand on it with your heel right at the back. Look at the space in front of your toes. If your toes are right at the edge, the shoe is too small. You want about a thumb’s width of extra space at the front. This extra room keeps your toes safe when you are stepping down steep rocks.

Wear your actual hiking socks

Don’t test new shoes using thin cotton socks you wear to work. Grab the thick wool socks you actually plan to wear on the trail. Brands like Bridgedale or Smartwool make thick cushioned socks that take up a lot of volume inside the shoe. If you size your shoes with thin socks, they will be way too tight once you put on your proper gear. I once forgot my hiking socks and tried on boots in trainer liners; the boots I bought were useless once I got home and geared up properly.

Check the width and volume

Length isn’t everything. Some of us have “high volume” feet, meaning the top of the foot sits high, or we have wide balls of the feet. If the shoe feels tight across the widest part of your foot, don’t assume it will stretch. Synthetic hiking shoes don’t stretch much at all. Leather ones might soften, but they won’t grow a size. If you feel “pinched” now, you’ll feel “crushed” later.

The finger test at the heel

Put the shoe on but don’t tie the laces yet. Slide your foot forward until your toes touch the very front. Try to slide your index finger down behind your heel. It should fit snugly but easily. If you can’t get your finger in, the shoe is too short. If you can fit two fingers back there, your foot will likely slide around too much, which leads to nasty blisters on your heels.

Test the shoes on an incline

Most good outdoor shops have a small wooden ramp or a set of stairs. Use them. Walk up and down. When going uphill, your heel shouldn’t lift out of the back of the shoe more than a tiny bit. When going downhill, your toes should not hit the front of the shoe. If your toes touch the end while walking down a ramp, you need to go up half a size or try a different brand with a deeper toe box.

I’ve noticed that different brands have very specific fits. Here is a quick look at what I’ve found over the years:

Brand	Common Fit Style	Best For
Salomon	Narrow and snug	Fast hiking / narrow feet
Merrell	Wide toe box	Comfort out of the box
Meindl	Traditional and roomy	Wide feet / heavy trekking
La Sportiva	Narrow and technical	Scrambling and rocky paths

Common sizing mistakes to avoid

• Ignoring the “break-in” period: Even a perfectly sized leather boot feels stiff at first. Don’t confuse stiffness with a bad fit.
• Sticking to your “number”: I wear a 9 in trainers, a 9.5 in Salomon, and a 10 in some Italian boots. Forget the number; trust the feel.
• Lacing too loose: When testing, lace them up properly. A loose lace can make a shoe feel too big when it’s actually just not secured.

Frequently Asked Questions (FAQs)

Should hiking shoes be a size bigger?

Usually, yes. Most hikers find that going up half a size or one full size from their street shoe size provides the necessary room for thick socks and foot swelling. It also prevents your toes from hitting the front on descents.

How much gap should be in the front of a hiking shoe?

You should aim for roughly 1cm to 1.5cm of space. A good rule of thumb is being able to fit one finger behind your heel when your toes are touching the front of the unlaced shoe.

Is it better for hiking shoes to be tight or loose?

Neither. If they are too tight, you get bruised toes and poor circulation. If they are too loose, your foot slides, causing friction and blisters. They should feel snug around the midfoot but wiggle-room-ready at the toes.

How do I know if my hiking shoes are too small?

If your toes touch the end of the shoe while walking on flat ground, or if they cramp up when you walk down a hill, they are definitely too small. You should also check for any pinching on the sides of your pinky toe.

Do hiking shoes stretch over time?

Leather boots will mould to your foot shape and soften, but they won’t gain significant length. Synthetic shoes and trail runners hardly stretch at all. Always buy for the fit you feel in the shop, not the fit you hope for later.

Getting the right fit is the difference between a great day on the fells and a miserable walk back to the car. If you take the time to measure late in the day and use the insole test, you’ll know exactly how to size hiking shoes for your next adventure.