I am in the process of trying to buy my first pair of mountaineering boots. I believe I am going to try to get the Scarpa Summit GTX boot, because of how well all different types of Scarpa Boots and Shoes have fit me in the past. The craftsmanship is known etc, nothing against those Trangos everyone seems to be in love with. Anyway I am just trying to figure out what size is best to get. How many sizes bigger than my hiking boots to I go? The Scarpa's come in Euro Sizes, but that doesn't really matter, just wondering how much bigger most peoples Mountaineering boots are than their standard hikers. Thanks

I am running the Scarpa Freneys in size 42. My Scarpa hiking boots are 42.5. I bought both sets of boots within a year of each other. I wear mountaineering smartwool socks in both boots. I don't double up in either pair.
My shoe size in American standards is 9 1/2.
Hope this helps.

I don't go bigger. I buy them to fit. My old double plastics were bought 1/2 size big, which I have regretted since the first time I used them on a technical pitch.

mconnell is right.. exactly how my ice boots ended up being smaller in numerical size than my hikers

For general purpose mountaineering you want to make sure that you have enough room in the front of the boot that your toes don't slide into the front of the boot when the boots are properly laced and you are going downhill. That may or may not be bigger than your hiking boot size and may or may not be bigger than what you'd want for technical ice - it depends on the last for the boot and the shape of your foot. The only good thing about descending 10K' down the mountain when your toes are hitting the front of the boot is that you can gross out your friends by showing them how your blackened toenails are falling off.

If you want to use them for mountaineering, you will probably end up a half size larger than your usual shoe.
Try them on with the socks you expect to use. If you will be on tall mountains in cold temperatures, the socks will take up some volume. Some people talk about how many fingers they can stick in the ankle with the boot on, but I have no idea what they are talking about.
If you want to use them in the afternoon to do technical ice climbing or on low altitude peaks, your feet will get a little sweaty with all those socks on. If that's what you want, go with a smaller boot or just get two different liners.
I normally wear a size 9. My double plastics are size 9.5. I've used them a bit and never hurt my little toenails. I cut my toenails frequently. People who try to sell me ski boots tell my I should be in 8.5 US (after converting the size).

JHH60 wrote:For general purpose mountaineering you want to make sure that you have enough room in the front of the boot that your toes don't slide into the front of the boot when the boots are properly laced and you are going downhill. That may or may not be bigger than your hiking boot size and may or may not be bigger than what you'd want for technical ice - it depends on the last for the boot and the shape of your foot. The only good thing about descending 10K' down the mountain when your toes are hitting the front of the boot is that you can gross out your friends by showing them how your blackened toenails are falling off.

Cure that problem by finding a boot that fits you correctly, not by buying them too big.

mconnell wrote:

JHH60 wrote:For general purpose mountaineering you want to make sure that you have enough room in the front of the boot that your toes don't slide into the front of the boot when the boots are properly laced and you are going downhill. That may or may not be bigger than your hiking boot size and may or may not be bigger than what you'd want for technical ice - it depends on the last for the boot and the shape of your foot. The only good thing about descending 10K' down the mountain when your toes are hitting the front of the boot is that you can gross out your friends by showing them how your blackened toenails are falling off.

Cure that problem by finding a boot that fits you correctly, not by buying them too big.

Exactly my point.