Under Armour kids sizing transitions through four distinct phases including a youth alpha system (YXS, YSM, YMD, YLG, YXL) that replaces numeric sizes. The standard fit is the most generous of the three major sportswear brands.
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Size recommendations are based on official brand size charts and are provided as a guide only. Fit may vary by item, style, and individual child. Outgrow is not responsible for sizing decisions made based on these recommendations.
Does Under Armour Kids Run Big or Small?
At 112cm our reference child fits UA size 6 with a waist of 57–60cm — the most generous range of the three sportswear brands, with up to 6.5cm of room above the reference measurement.
| Brand | Size | Waist (cm) | Hip (cm) | vs ref child |
|---|---|---|---|---|
| Under Armour | 6 | 57–60 | 62–65 | +3.5–6.5cm waist |
| Nike | 6 | 57–58.5 | 62–65 | +3.5–5cm |
| Adidas | 5-6Y / 2XS | 56 | 64 | +2.5cm |
| Zara Kids | 111–116 | 55 | 62 | +1.5cm |
| H&M | 116 | 54 | 60 | +0.5cm |
| Old Navy | 6 | 53 | — | Average |
The 57–60cm waist range for UA size 6 is notably wide — a 3cm spread within a single size, reflecting performance wear design for movement. For the full methodology see our cross-brand sizing research. See also our complete kids clothing size chart comparing 36+ brands side by side.
UA Youth Sizing System (YXS–YXL)
From approximately 119cm UA switches to Y-prefix alpha sizes. There is no size 7, 8, 10 or 12. The transition is clean for boys (size 6 ends at 118cm, YXS starts at 119cm) but girls have a partial overlap between 6X (118–123cm) and YXS (119–130cm).
UA Boys Tops
| Size | Height (cm) | Chest (cm) | Weight (kg) |
|---|---|---|---|
| 0-3M | 52–61 | 39–43 | 3–6 |
| 3-6M | 61–69 | 43–46 | 6–7 |
| 6-9M | 69–74 | 46–47 | 7–9 |
| 12M | 74–77 | 47–48 | 8–10 |
| 18M | 77–84 | 48–51 | 10–12 |
| 24M | 84–89 | 51–53 | 12–14 |
| 2T | 84–89 | 51–53 | 13–15 |
| 3T | 89–97 | 52–55 | 14–16 |
| 4 / 4T | 97–104 | 55–57 | 16–18 |
| 5 | 104–112 | 57–60 | 17–19 |
| 6 | 112–118 | 60–62 | — |
| 7 | 118–127 | 62–66 | — |
| YXS | 119–128 | 63–66 | — |
| YSM | 128–135 | 66–69 | — |
| YMD | 135–150 | 69–74 | — |
| YLG | 150–165 | 74–83 | — |
| YXL | 165–178 | 83–90 | — |
Size 7 and YXS overlap at 118\u2013128cm. YXS is the youth alpha equivalent.
Boys Tops — Plus
| Size | Height (cm) | Chest (cm) |
|---|---|---|
| YSM Plus | 128–135 | 70–74 |
| YMD Plus | 135–150 | 74–79 |
| YLG Plus | 150–165 | 79–88 |
| YXL Plus | 165–178 | 88–95 |
UA Girls Tops
| Size | Height (cm) | Chest (cm) | Weight (kg) |
|---|---|---|---|
| 0-3M | 52–61 | 39–43 | 3–6 |
| 3-6M | 61–69 | 43–46 | 6–7 |
| 6-9M | 69–74 | 46–47 | 7–9 |
| 12M | 74–77 | 47–48 | 8–10 |
| 18M | 77–84 | 48–51 | 10–12 |
| 24M | 84–89 | 51–53 | 12–14 |
| 2T | 84–89 | 51–53 | 13–15 |
| 3T | 89–97 | 52–55 | 14–16 |
| 4 / 4T | 97–104 | 55–57 | 16–18 |
| 5 | 104–112 | 57–60 | 17–19 |
| 6 | 112–118 | 60–62 | — |
| 6X | 118–123 | 62–64 | — |
| YXS | 119–130 | 63–67 | — |
| YSM | 130–135 | 69–70 | — |
| YMD | 135–149 | 70–77 | — |
| YLG | 149–160 | 77–86 | — |
| YXL | 149–160 | 86–91 | — |
Girls 6X (118\u2013123cm) and YXS (119\u2013130cm) overlap. YLG and YXL share the same height range (149\u2013160cm).
Girls Tops — Plus
| Size | Height (cm) | Chest (cm) |
|---|---|---|
| YSM Plus | 130–135 | 72–74 |
| YMD Plus | 135–149 | 74–83 |
| YLG Plus | 149–160 | 83–89 |
| YXL Plus | 149–160 | 89–94 |
UA Boys Bottoms
| Size | Height (cm) | Waist (cm) | Hip (cm) | Weight (kg) |
|---|---|---|---|---|
| 2T | 84–89 | 52–55 | — | 13–15 |
| 3T | 89–97 | 53–56 | — | 14–16 |
| 4 / 4T | 97–104 | 55–57 | — | 16–18 |
| 5 | 104–112 | 56–58 | — | 17–19 |
| 4 | 97–104 | 55–57 | 57–60 | — |
| 5 | 104–112 | 56–58 | 60–62 | — |
| 6 | 112–118 | 57–60 | 62–65 | — |
| 7 | 118–127 | 58–61 | 65–67 | — |
| YXS | 119–128 | 58–61 | 66–69 | — |
| YSM | 128–135 | 61–63 | 69–71 | — |
| YMD | 135–150 | 63–69 | 71–79 | — |
| YLG | 150–165 | 69–76 | 79–86 | — |
| YXL | 165–178 | 76–84 | 86–94 | — |
Toddler rows (2T\u20135) list weight. Little kids/youth rows (4\u2013YXL) list hip.
Boys Bottoms — Plus
| Size | Height (cm) | Waist (cm) | Hip (cm) |
|---|---|---|---|
| YSM Plus | 128–135 | 69–71 | 74–77 |
| YMD Plus | 135–150 | 71–79 | 77–85 |
| YLG Plus | 150–165 | 79–86 | 85–93 |
| YXL Plus | 165–178 | 86–94 | 93–100 |
UA Girls Bottoms
| Size | Height (cm) | Waist (cm) | Hip (cm) | Weight (kg) |
|---|---|---|---|---|
| 2T | 84–89 | 52–55 | — | 13–15 |
| 3T | 89–97 | 53–56 | — | 14–16 |
| 4 / 4T | 97–104 | 55–57 | — | 16–18 |
| 5 | 104–112 | 56–58 | — | 17–19 |
| 4 | 97–104 | 55–57 | 57–60 | — |
| 5 | 104–112 | 56–58 | 60–62 | — |
| 6 | 112–118 | 57–60 | 62–65 | — |
| 6X | 118–123 | 58–60 | 65–66 | — |
| YXS | 119–130 | 58–61 | 66–71 | — |
| YSM | 130–135 | 61–62 | 71–74 | — |
| YMD | 135–149 | 62–67 | 74–83 | — |
| YLG | 149–160 | 67–77 | 83–93 | — |
| YXL | 149–160 | 77–83 | 93–98 | — |
Girls 6X and YXS overlap at 119\u2013123cm. YLG and YXL share height range (149\u2013160cm) \u2014 use waist/hip to differentiate.
Girls Bottoms — Plus
| Size | Height (cm) | Waist (cm) | Hip (cm) |
|---|---|---|---|
| YSM Plus | 130–135 | 69–71 | 79–81 |
| YMD Plus | 135–149 | 71–79 | 81–88 |
| YLG Plus | 149–160 | 79–88 | 88–97 |
| YXL Plus | 149–160 | 88–91 | 97–100 |
UA Kids Shoe Size Chart
UA uses K suffix for infant/toddler shoes transitioning to Y suffix for older kids at US 1Y / EU 32 / 20cm foot length.
| US | EU | UK | Foot length (cm) |
|---|---|---|---|
| 1K | 16 | 0.5 | 7.0 |
| 2K | 17 | 1.5 | 8.0 |
| 3K | 18.5 | 2.5 | 9.0 |
| 4K | 19.5 | 3.5 | 10.0 |
| 5K | 21 | 4.5 | 11.0 |
| 6K | 22 | 5.5 | 12.0 |
| 7K | 23.5 | 6.5 | 13.0 |
| 8K | 25 | 7.5 | 14.0 |
| 9K | 26 | 8.5 | 15.0 |
| 10K | 27 | 9.5 | 16.0 |
| 11K | 28 | 10.5 | 17.0 |
| 12K | 30 | 11.5 | 18.0 |
| 13K | 31 | 12.5 | 19.0 |
| 1Y | 32 | 13.5 | 20.0 |
| 2Y | 33.5 | 1.5 | 21.0 |
| 3Y | 35 | 2.5 | 22.0 |
| 4Y | 36 | 3.5 | 23.0 |
| 5Y | 37.5 | 4.5 | 23.5 |
| 6Y | 38.5 | 5.5 | 24.0 |
| 7Y | 40 | 6 | 25.0 |
Frequently Asked Questions
Does Under Armour kids run big or small?
UA runs the most generous standard fit in the waist of the three major sportswear brands. At 112cm, size 6 has a waist of 57–60cm — up to 6.5cm above our reference child’s 53.5cm measurement. No slim fit is available.
What is Under Armour Youth sizing?
Youth sizing (YXS, YSM, YMD, YLG, YXL) replaces numeric sizes from approximately 119cm onwards. There are no sizes 7, 8, 10 or 12 in UA’s older kids range — the Y-prefix system handles all older kids sizing.
How does Under Armour compare to Nike kids sizing?
Both run generous compared to fashion brands. UA (waist 57–60cm) is slightly more generous than Nike (57–58.5cm) at 112cm. Both cover the 116–122cm range that Adidas skips.
What age is Under Armour YXS?
YXS covers 119–128cm for boys and 119–130cm for girls. Most children reach 119cm around age 7–8. Always use height rather than age.