How to Choose the Right Shoe Size Online (Plus 7 Mistakes)

Buying shoes online is convenient, but you cannot try them on first. Half a size off is already enough to squeeze the top of your foot or let your heel slip out after a few weeks. This guide combines the at-home measuring method, the 7 most common sizing mistakes, and a point few articles mention: a wrong-size pair wears out faster than one that fits.

Why shoe sizes are less reliable than you think

• Feet change over time: age, weight gain and water retention all shift your measurements. Last year's size may no longer be right today.
• Small gaps, real consequences: half a size is roughly 0.3cm and a full size about 0.7cm — just enough to rub your heel or press on your toes.
• Every brand has its own chart. A size 41 from one brand is not always a size 41 from another, so always match your centimetre measurement against each brand's conversion table.

How to measure your feet at home, in 6 steps

Prepare a sheet of A4 paper, a pen and a ruler. Measure in the late afternoon or evening, when your feet are at their largest after a full day, and wear the socks you normally pair with those shoes.

1. Place the paper on a hard floor against a wall. Stand with your heel touching the wall.
2. Hold the pen upright and mark two points: the back of your heel and the tip of your longest toe.
3. Measure the distance between the two points in centimetres.
4. Repeat on the other foot.
5. Use the longer foot as your reference. A half-size difference between feet is normal.
6. Compare your centimetres with the brand's size chart. If you fall between two sizes, go for the larger one.

7 common mistakes when choosing a size

1. Not measuring before buying. In a store, ask the staff to measure your feet on a Brannock device instead of estimating.
2. Confusing width with volume. After lacing up, try sliding two fingers between the eyelets. One finger means too loose, three means too tight, two is about right.

3. Avoiding the upsize. Feet do not shrink to order. Half a size of extra room beats half a size of squeezing every time. 4. Buying to please friends. Compliments on the colour do not make the shoe fit your foot. For shoes you walk in all day, feel beats looks. 5. Trusting reviews blindly. Check whether the reviewer has a similar foot shape and usage, and remember that some reviews are sponsored by brands. 6. Holding on to worn-out pairs. After roughly 500–800km, running shoes lose their cushioning and the tread wears flat. Worn pairs make your feet ache and speed up uneven wear. 7. Skipping specialist shops. Running stores often analyse your gait, which helps you pick the right width and sole type for how you actually move.

The wrong size wears shoes out faster

This is the part few articles mention, yet it decides how long your pair lasts:

• Too tight: the leather and stitching stay stretched around the toe box. A few months later, the toe glue starts to lift and stitches break off one by one.
• Too loose: your foot slides forward with every step. The heel rubs the lining and the sole touches the ground unevenly, wearing down one side first.
• Uneven wear does not fix itself. The longer you keep wearing the pair, the more the sole tilts and the easier the glue line opens. See our guide on why soles wear unevenly.
• Choosing the right size from the start is cheaper than repairing later. For a pair you already own, early sole protection slows down wear on the contact area.

When should you send your shoes to EXTRIM?

Shoes with lifted toe glue, torn stitching from a tight fit, or a heavily worn heel and uneven sole are worth repairing before you give up on them. EXTRIM's shoe repair service covers body stitching (200,000–350,000 VND), toe or heel regluing (250,000–400,000 VND) and edge reinforcement (250,000 VND) — 2026 reference prices, confirmed after inspection.

👉 Send photos of your worn pair for advice

Public case studies

Photos in this article illustrate the process — they are not a before–after record with a public case code. EXTRIM does not use illustrative images to promise results for every pair.