Size Guide (Sizing & Fit)
Find Your Perfect Fit for Cozy Comfort at Every Age.
💡 Quick Fit & Safety Tips
- Safety First: In accordance with CPSC guidelines, our sleepwear is designed to fit snug against the skin for fire safety, without using harsh chemical flame retardants.
- Designed to Last 3x Longer: Thanks to our ultra-stretchy, breathable fabric and fold-over foot/hand cuffs, your baby can often stay in their current size longer than traditional cotton sleepwear.
- Between Sizes? If your child is at the top of the weight/height range, or if you prefer a roomier fit, we recommend sizing up.
1. Baby & Infant Sleepwear (Zippies & Sleepwear)
Features extra stretch, fold-over hand cuffs (on select sizes), and fold-over foot cuffs to transition from footie to romper.
| Size | Age / Range | Height (in) | Height (cm) | Weight (lbs) | Weight (kg) |
| Micro Preemie | Preemie | Up to 17" | Up to 43 cm | Up to 4 lbs | Up to 1.8 kg |
| Preemie | Preemie | Up to 18" | Up to 46 cm | 4 – 6 lbs | 1.8 – 2.7 kg |
| Newborn (NB) | 0 – 1 Month | 18" – 21.5" | 46 – 55 cm | 6 – 9 lbs | 2.7 – 4.1 kg |
| 0 - 3 Months | 0 – 3 Months | 21.5" – 24" | 55 – 61 cm | 9 – 13 lbs | 4.1 – 5.9 kg |
| 3 - 6 Months | 3 – 6 Months | 24" – 26.5" | 61 – 67 cm | 13 – 17 lbs | 5.9 – 7.7 kg |
| 6 - 12 Months | 6 – 12 Months | 26.5" – 29.5" | 67 – 75 cm | 17 – 22 lbs | 7.7 – 10 kg |
| 12 - 18 Months | 12 – 18 Months | 29.5" – 32.5" | 75 – 82 cm | 22 – 26 lbs | 10 – 11.8 kg |
| 18 - 24 Months | 18 – 24 Months | 32.5" – 35.5" | 82 – 90 cm | 26 – 30 lbs | 11.8 – 13.6 kg |
2. Toddler & Kids Two-Piece Pajama Sets
Designed with a slim, snug-fitting silhouette for safe sleeping. Soft elastic waistbands and stretchy ankle cuffs allow for easy movement.
| Size | Height (in) | Height (cm) | Weight (lbs) | Weight (kg) | Fit Recommendation |
| 12 - 18M | 29.5" – 32.5" | 75 – 82 cm | 22 – 26 lbs | 10 – 11.8 kg | Snug fit |
| 18 - 24M | 32.5" – 35.5" | 82 – 90 cm | 26 – 30 lbs | 11.8 – 13.6 kg | Snug fit |
| 2T | 33" – 36" | 84 – 91 cm | 28 – 31 lbs | 12.7 – 14.1 kg | True to size |
| 3T | 36" – 39" | 91 – 99 cm | 31 – 35 lbs | 14.1 – 15.9 kg | True to size |
| 4T | 39" – 42" | 99 – 107 cm | 35 – 40 lbs | 15.9 – 18.1 kg | True to size |
| 5/6 | 42" – 47" | 107 – 119 cm | 40 – 50 lbs | 18.1 – 22.7 kg | True to size |
| 7/8 | 47" – 52" | 119 – 132 cm | 50 – 65 lbs | 22.7 – 29.5 kg | Size up if taller |
| 10/12 | 52" – 58" | 132 – 147 cm | 65 – 85 lbs | 29.5 – 38.5 kg | Size up if taller |
3. Baby Wearable Blankets / Sleep Sacks (TOG Rated)
Wearable blankets replace loose blankets in the crib for safer sleep. Choose based on length and weight for the most secure neck/armhole fit.
| Size | Age Range | Baby Height | Baby Weight | TOG Recommendation |
| Small (S) | 0 – 6 Months | 21" – 28" (53–71 cm) | 10 – 18 lbs (4.5–8.2 kg) | Select TOG based on room temp |
| Medium (M) | 6 – 18 Months | 28" – 34" (71–86 cm) | 18 – 26 lbs (8.2–11.8 kg) | Select TOG based on room temp |
| Large (L) | 18 – 36 Months | 34" – 40" (86–102 cm) | 26 – 36 lbs (11.8–16.3 kg) | Select TOG based on room temp |
4. TOG Rating & Temperature Guide
TOG (Thermal Overall Grade) is an international standard measurement for a fabric's thermal resistance. It tells you how warm a wearable blanket or sleep sack is. The higher the TOG rating, the warmer the garment. Choose the right TOG based on your baby's nursery temperature rather than the season outside:
| TOG Rating | Nursery Temp (°F & °C) | Season / Feel | What Baby Should Wear Underneath |
| 0.5 TOG | 75°F–81°F (24°C–27°C) | Warm / Summer | Short-sleeve bodysuit or diaper only |
| 1.0 TOG | 69°F–74°F (21°C–23°C) | Moderate / Year-Round | Short-sleeve bodysuit or long-sleeve sleepsuit |
| 1.5 TOG | 68°F–73°F (20°C–23°C) | Ideal / Spring & Autumn | Long-sleeve bodysuit or footie pajama |
| 2.5 TOG | 61°F–68°F (16°C–20°C) | Cool / Autumn & Winter | Long-sleeve footie pajama + bodysuit layer |
| 3.5 TOG | Below 60°F (Below 16°C) | Cold / Chilly Winter | Warm long-sleeve pajama + thermal layer |
Safe Sleep & TOG Tips
- Check the Nape of the Neck: To check if your baby is too warm or cold, touch the back of their neck or chest. It should feel warm and dry. Cool hands and feet are normal for babies and do not mean they are cold.
- Never Overdress: Overheating is a risk factor for SIDS. Do not add extra blankets or quilts inside or over the wearable blanket.
- Adjust for Climate: If you use air conditioning or heating in the nursery, always select the TOG based on the actual room temperature inside the nursery.
📏 How to Measure Your Child
To choose the most accurate size, we recommend measuring your baby using a soft tape measure:
- Height: Lay your baby flat on a smooth surface and measure from the top of the head down to the bottom of the heel.
- Chest: Wrap the tape measure under your child’s arms around the fullest part of their chest.
- Weight: Weight is often the most accurate indicator for baby sleepwear sizing. Always prioritize weight over age!
❓ Frequently Asked Questions about Sizing
Q: Do these run true to size?
A: Yes! However, because of our signature ultra-stretchy fabric, many parents find our sleepwear fits longer than traditional 100% cotton brands.
Q: Why is the sleepwear snug-fitting?
A: U.S. safety standards require children's sleepwear to be either flame-retardant treated or snug-fitting. We choose snug-fitting natural fabrics so we never have to treat our clothes with harsh chemicals.
Q: What if I’m still unsure about the size?
A: We are here to help! Reach out to our Customer Care Team at support@yoofoss.com with your baby’s current age, height, and weight, and we'll help you pick the perfect size.