Adidas Ultraboost 5
Sizing & fit guide
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The converter shows the chart-equivalent size. The verdict above tells you whether to adjust from there for this specific model.
Why the Adidas Ultraboost 5 fits this way
The Adidas Ultraboost 5 is a knit-upper daily trainer, and the harvest signal is mixed-but-true-to-size with a lean toward sizing up for room. One runner: "I have two pairs of UBs and went .5 up on both. I'm a TTS 12 but went with a 12.5" — sizing up for the snug Primeknit. Another keeps the same number across the line: "All of my Nikes are size 10, most of my Adidas are 9.5" (i.e. Adidas a half down from Nike, with the Ultraboost in line with their other Adidas).
The defining feature is the Primeknit sock-like bootie, which wraps the foot closely. At true size it's a secure, compressive fit; wide-foot or high-volume runners feel the squeeze and are the main candidates for a half up. The Boost midsole and knit give a little with wear, but the bootie's width is fixed, so genuinely wide feet should size up rather than expect it to stretch.
Net: true to size for standard feet who like a snug running fit; size up a half for wide/high-volume feet or a roomier feel. Remember Adidas generally runs about a half size larger-numbered than Nike (you take a smaller Adidas number), so convert from your Nike size accordingly. Confidence is low given limited direct UB5 posts.
Common scenarios
I wear US 10 in Nike running shoes. What size Ultraboost 5?
About US 9.5 — Adidas generally runs a half size down in number from Nike. Take your true Adidas size; go up a half if you have wide feet or want room.
The Primeknit feels tight. Should I size up?
The knit bootie is snug by design at true size. If it's uncomfortable or you have wide/high-volume feet, size up a half — the bootie's width doesn't stretch much.
TTS or half up?
TTS gives a secure, compressive run fit; ½ up gives room for wide feet or a relaxed feel. Most standard feet are fine at true size.
How it compares to other models
- Adidas Forum Low Low confidence
Wearers report the same number in the Ultraboost and Forum
- Nike Pegasus 41 Low confidence
Both daily trainers run true to size; the Ultraboost's knit bootie is snugger than the structured Pegasus
- r/RunningShoeGeeks — Ultraboost sizing compared to other sneakers
- r/RunningShoeGeeks — Ultraboost size vs Nike/Yeezy
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