A typical 4-year-old boy may wear 4T or size 4, depending on his measurements and whether he's still in training pants. 4T suits children roughly 99 to 104 cm who still need diaper ease through the seat. Size 4 covers the same height range but with a slimmer, longer cut built for potty-trained children. Always measure height, chest, and waist before choosing, since age alone is a starting point. If he's on the border, size up.

4T is a toddler size, built with a shorter inseam and extra room through the seat and belly for children still in diapers. Size 4 is the first numeric kids' size, featuring longer sleeves and legs, a slimmer torso, and no diaper ease. Both cover a similar height range, roughly 99 to 106 cm, but their body shapes differ. The right choice comes down to your son's build and potty-training status. When in doubt, compare chest and inseam measurements.

Use a soft measuring tape, never a metal ruler or rigid tape. Measure height with your son standing barefoot against a wall, heels flat, looking straight ahead, and record it in centimetres. Measure chest around the fullest part, tape flat and horizontal under the arms, not pulled tight. Measure waist around the natural waistline, just above the navel, snug but not pinching. Compare all three numbers to the size chart on this page and to the product's fit notes.

Sizing up is generally safe for pyjamas, since fit tolerance runs wider than for structured clothing like suits or dress shirts. Boys in active growth phases, typically ages 4 to 5 and 9 to 12, can outgrow a size within 3 to 4 months, so sizing up buys extra wear time. Snug-fit cotton styles have less stretch and should be sized to your measurements rather than automatically bumped up. Relaxed or fleece styles allow more room to size up comfortably.

Boys aged 8 to 10 typically fall into sizes 8 to 10, corresponding roughly to heights of 128 to 140 cm. Growth rates vary widely at this age, so two boys of the same age can differ by a full size. Measuring height and chest confirms the right fit: size 8 suits boys around 128 to 133 cm, while size 10 suits those around 133 to 140 cm. Waist is worth checking too, especially in woven or flannel styles.