"Running shoes should be a whole size up" ??

You’re at a shoe store, who cares what size you wore/measured at. Try on shoes and see how they feel. try jogging in them. Try on a bigger size if your normal size is too small. Buy what fits best.

Don't be a dummy, the shoe guy is telling new runners to buy the shoe a full size bigger than what fits at the store.

I posted above that my normal size is a full size up from the Brannock, and that my forefeet are wide (bunions). To add to more context for that that, I size up that much NOT because my feet swell up, because my feet, at least, don't swell a noticeable amount. For me, it's that any less than a full size up, my toes will come into contact the front of the shoe. Maybe not every toe, but contact is enough that that it will bruise the tips of some toe, which might be merely uncomfortable on longer runs, but may also callous the tips of those toes, or damage a toenail(s), which I already keep as short as I can cut them. Uncomfortable toes is reason enough for me to size up until there's zero pressure.

Why do shoes smaller than a full size up contact the tips of my toes? I suspect it's because Brannock sizing doesn't take into account the shape of the front of shoes, just the longest point of the toe. I don't have any shoes that perfectly trace the shape of my toes, they all are pointy. I don't squeeze a toe into that point because the rest of the toes would be crushed tight against the front of the toebox. That's part of the thumbnail clearance recommendation frequently stated. Also, the upper shortens when you flex the forefoot of the shoe on toe-off. A thumbnail of space with the shoe flat closes out to close to zero clearance when my feet flexes onto your toes... try squatting down onto your tippy toes and feel the clearance go away.

If sizing the shoe smaller works for you, that's not my business. Your feet are a different shape than mine and interacts with the shape of your shoes differently. It's also a personal preference to some extent. I changed my preference and started going with larger sizing when I hit about 30, when I realized how much more comfortable it was. I should have sized it that way all along though because then maybe I wouldn't have bunions now (bunions are bone growth thought to be induced by pressure from tight shoes). I grew up thinking tight shoes were normal, and was afraid to size up for fear of having clown shoes/looking weird. There were cultural issues there, with my parents joking about shoes that were too big (this was '70s, '80s) that make no sense to me now.

I've worked at a shoe store and I've commonly sold people shoes different than the size they previously wore both bigger and smaller. Unless you were there and could tell me the Brannock measurement, what he wore before, and what he was recommended, then we can't really draw any conclusions from this story.

I specifically said I don't recommend what worked for me: going up a half-size (w thick socks.)

When you're desperate to get a thing fixed you might try some "unrecommended" move. I did. It worked. For me.

This.

My local place lets people that are trying on shoes run in the park that is adjacent to their shop. They get a lot of my business because they know what they're doing and I want them to stay around. Sure I could save a few bucks buying online, and sometimes I do but I still try to support them whenever I can.

Half sizes? I thought they only have those in children’s sizes. I wear 13/14 but have never seen a 13.5.

I'm a 9.5 on a Brannock, which is what I wear for most dress shoes, though I wear 9 for loafers.

Running shoes I'm a 10.5 or 11. I have made the mistake of wearing 10s before, and they quickly became extremely painful. Pinching in the arch, hot spots on the instep.

Soccer shoes, I'm an 8.5 in natural leather, but they stretch a lot. (Synthetics are awful.)

all my running shoes are 1 to 1.5 sizes bigger than my dress shoes. not because I want extra room for running but because that’s the size that fits properly. If I were to wear them as a casual sneaker I’d buy them in the exact same size.

Not many shoe companies make half sizes above size 13. However, some companies (like Asics) will have 13.5 available in specific models. These are tough to find in-store, similar to widths like 4E.

I manage a running store for 6 years, and the sizing question is always a fun one. Every running specialty shop is different, but if it is part of a chain then there is a good bet that they will recommend you sizing up by a full size. There are a lot of reasons for this, some of them good and some bad. I'll share a few below:

1. Consistency. A running specialty chain needs to offer relatively consistent advice. If one associate says "size up half a size" and the other one says "size up a full size", then the customer will begin to assume no one really knows what they are talking about. Moreover, when a specialty chain has to train 100 associates a year across multiple locations, the experience should be somewhat consistent. Training one store in Austin, TX to add one full size to a brannock measurement, then another in Houston, TX to add half a size and another in El Paso, TX to not add any length at all, creates a very inconsistent shopping experience for your customer base.

2. The swelling thing. I can't think of a single serious runner that believes their foot somehow elongates a full inch during the course of a training run, thereby causing them to suddenly hit the front of their shoe (the toeguard). However, you know what does often happen? A foot that feels quite snug in the store, can suddenly start feeling a bit tighter after an hour of pounding the pavement. That one spot that may or may not have felt tight in the store, actually begins to hurt. Now think about the shape of a shoe, and remember that the front of the shoe that tapers towards the toe is easily the most narrow. Keeping that foot from being crammed all the way into that area makes it less likely for the shoe to start hurting on the first long run and come back to the store as a return.

3. Your feet aren't the same size. I can't tell you how many feet I've sized in a brannock device. More often than not, one foot will be 1/8 to 1/4 size longer than the other. That could be because the arch has fallen a hair over time, a broken bone at a young age, or most commonly that one foot is just plain longer than the other. A good shoe fitter will know to recommend a size based on the longer foot. Your shorter foot may size for a size 8, and the longer may size for an 8 1/4 on the brannock. Unless you are being fit for a track spike (which should fit quite snug), the safe recommendation is between a size 8.5 - 9. If you're used to wearing a size 8 in your casual shoes, a size 9 will sound insane. However to the guy looking at your foot sitting in the brannock, anything smaller than an 8.5 is going to result in that shoe coming back to the store about a week later.

At the end of the day, an experienced runner knows what works for them. The store you go to may start out recommending a full size up, but good runners that work as "shoe dogs" will work with you to find something that feels right. If they argue with you or tell you that you absolutely have to go a full size up, they are being unreasonable and you should walk right out the door.

Shoes stretch out over the course of normal use. I like no more than a c*nt hair of space before the big toe.

All you people mentioning a Brannock. I worked at a shoe store so knew it's name. Do regular people know the name of this thing, or have we all sold shoes?

Natural materials stretch and break in. Synthetic materials don’t. Do you wear leather running shoes?

Wearing shoes that are too small either causes or exacerbates many common running injuries... Morton's Neuroma, black toenail, bunions, metatarsal stress fractures, blisters, top of foot bruising and more. I wear running shoes a full size larger than my dress shoes. 

I know the name of the device, and I've never sold shoes.

After you run in a new shoe, the foam in EVA sockliners (not the Ortholite type) and midsole compresses a little bit and forms to your feet. I can feel the indents from my toes and ball of feet in the sockliner and sometimes even midsole even after a single 10 mile run from new. That creates a bit more upper volume, loosening up the shoe a bit, but it's noticeable mostly in width for me. Maybe for someone who sizes their shoes like @Runtodafridge, it's noticeable in length too.

In the past I've had cycling shoes that were a bit tight. I put the cycling shoes in my running shoes for one 10 mile run, and, putting them back in the cycling shoes, that loosened up the fit noticeably.

*put the sockliners of the cycling shoes in my running shoes for one 10 mile run

I’ve been running since elementary school. As long as I can remember all of my running shoes have been a size up from my dress shoes. And not because my feel swell but because of socks and movement. There is a swelling factor in the heat though and likely longer runs too.

For the past 20 years, I have worn a womens size 7 dress shoe. Depending on the brand, I’m an 8 or 8.5 in running shoes.

The number of smoothbrain bozos citing their own stinky feet as evidence that people don't need to size up is proof that the average IQ of a Let's Run user in below 75.