If you wanted to pick two mainstream brands that fit as differently as possible for the same label, Uniqlo and Old Navy would be a strong pairing. Uniqlo runs small — slim Japanese fit blocks, trim shoulders, short sleeves. Old Navy runs large, and not subtly: garments frequently measure a size or more over what the chart suggests, especially in women's tops, dresses, and jeans.
Here's the twist: the published charts don't look that far apart. Old Navy's chart sits roughly an inch bigger than Uniqlo's at the same letter — a normal-looking gap. The distance you actually feel comes from the garments: Uniqlo cuts close to its chart while Old Navy's vanity sizing means the clothes run beyond theirs. The tables below show the on-paper gap; the verdict covers the real-world one.
The short answer
Uniqlo runs smaller by a wide margin — the same letter can be two fits apart in practice
On the charts, Old Navy's women's measurements run about an inch bigger per letter (Uniqlo S covers a 33–34" bust, Old Navy S 34–35"), and its men's chart pulls further ahead at L and XL. In practice the gap is bigger: Uniqlo's slim cut delivers what its chart promises or less, while Old Navy garments often measure a size or more over the label — independent tests have found pants measuring inches larger than marked.
So the working rule has two steps, not one. If you wear Old Navy's generous fit and want the same easy feel at Uniqlo, go up one size, possibly two in slim-fit lines. Going the other way, your Uniqlo size at Old Navy will fit loose; for a fitted look at Old Navy most shoppers size down one from their true US size — meaning your Uniqlo label and your Old Navy label can easily end up two apart on the rack.
Uniqlo vs Old Navy at a glance
| Uniqlo | Old Navy | |
|---|---|---|
| Overall fit | Runs small — slim Japanese fit blocks, short sleeves and torso | Runs large — garments often measure a size or more over the label |
| Chart vs garment | Garments track the chart closely, cut slim | Vanity sizing — finished garments frequently exceed the chart |
| Where to adjust | Size up one from US brands; two in slim-fit lines | Size down one in fitted tops, dresses, and jeans |
| Basics | Consistent across categories once you know your size | Tees and sweats stay closer to true to size than fashion pieces |
| Denim | Bottoms sold by numeric waist size in inches | Runs big in waist and hip; stretch relaxes further with wear |
Women's body measurements side by side
Body measurements from each brand's published chart at the same letter. The on-paper gap is about an inch — the real-world gap is bigger, because Old Navy garments tend to measure over their chart while Uniqlo cuts slim to its own.
| Size | Uniqlo bust | Old Navy bust | Uniqlo waist | Old Navy waist |
|---|---|---|---|---|
| XS | 31–32" · 78–83 cm | 31–33" · 78.5–84 cm | 24–25" · 60–65 cm | 23–25" · 58.5–63.5 cm |
| S | 33–34" · 83–88 cm | 34–35" · 86.5–89 cm | 26–27" · 65–70 cm | 26–27" · 66–68.5 cm |
| M | 35–37" · 88–94 cm | 36–37" · 91.5–94 cm | 28–30" · 70–76 cm | 28–29" · 71–73.5 cm |
| L | 37–40" · 94–101 cm | 38.5–40.5" · 98–103 cm | 30–33" · 76–83 cm | 30.5–32.5" · 77.5–82.5 cm |
| XL | 40–43" · 101–109 cm | 42.5–45" · 108–114.5 cm | 33–36" · 83–91 cm | 34.5–37" · 87.5–94 cm |
| 2XL / XXL | 43–46" · 109–117 cm | 47.5" · 120.5 cm | 36–39" · 91–99 cm | 39.5" · 100.5 cm |
Men's tops side by side
Body chest measurements at the same letter. Old Navy's chart starts close to Uniqlo's at S–M but pulls two inches ahead by L — and Old Navy's roomy cut widens the gap further.
| Size | Uniqlo chest | Old Navy chest |
|---|---|---|
| S | 35–38" · 89–96.5 cm | 37–38" · 94–96.5 cm |
| M | 38–41" · 96.5–104 cm | 39–41" · 99–104 cm |
| L | 41–44" · 104–112 cm | 43–45" · 109–114.5 cm |
| XL | 44–47" · 112–119.5 cm | 47–49" · 119.5–124.5 cm |
Switching between Uniqlo and Old Navy
- Going Old Navy → Uniqlo: size up one as your default, and consider two in Uniqlo's slim-fit lines — Old Navy's generous garments make the jump feel bigger than the charts suggest.
- Going Uniqlo → Old Navy: your Uniqlo size will fit loose; for a fitted look, take your true US size minus one in Old Navy tops, dresses, and jeans.
- Treat basics differently: Old Navy tees and sweats run closer to true to size, so the size-down rule applies mainly to fitted and fashion pieces.
- In denim, the brands point opposite ways — Old Navy stretch jeans relax with wear (when between sizes, go smaller), while Uniqlo bottoms are sold by waist inches and cut trim.
Measurements are based on each brand's published size charts and may vary by garment, fabric, and region. For the full charts and fit notes, see the Uniqlo size guide and the Old Navy size guide.
Uniqlo vs Old Navy sizing FAQs
Which runs smaller, Uniqlo or Old Navy?
Uniqlo, by a lot. Uniqlo cuts slim on Japanese fit standards, while Old Navy is one of the most consistently generous-sizing mainstream brands — its garments often measure a size or more over the label. The same letter can fit like two different sizes between the two stores.
I wear a medium at Old Navy — what size at Uniqlo?
Start with a large. Uniqlo's chart medium covers a similar body to Old Navy's, but Uniqlo cuts trim to its chart while Old Navy garments run beyond theirs — so the fit you're used to at Old Navy in M lives closer to L (or slim-fit XL) at Uniqlo.
Are the size charts really that different?
Less than you'd expect — about an inch apart per letter in the women's bust, with Old Navy's men's chart pulling further ahead at L and XL. The fit difference comes mostly from the garments: Old Navy's vanity sizing means clothes measure over the chart, while Uniqlo's slim cut delivers the chart or less.
Should I size down at Old Navy if Uniqlo fits me true?
For fitted pieces, yes — tops, dresses, and jeans at Old Navy are usually safer one size down from your true US size, and stretch denim relaxes further with wear. Keep your usual size in Old Navy basics like plain tees and sweats, which run closer to true.
Which brand is the safer blind buy?
Uniqlo, once you've adjusted. Its fit blocks barely change between seasons, so a sized-up Uniqlo order lands predictably. Old Navy is generous and varies more between fitted pieces and basics, so check the product's fit description — and when in doubt, go down rather than up.
