How to measure kids for clothes: age, height or both

Use height first, then the chest for tops and dresses, or the waist and inseam for trousers, and the age last. That's the rule printed on the Ruban Size baby and toddler templates ("Choose by height first: age is only a guide"), and it's how Find my size weighs a child's measurements. A child of four and a half who is 108 cm tall gets a 5Y, not a 4Y.

How to measure a child

1. Height. Barefoot, back and heels against a wall, looking straight ahead. Lay a book flat on the top of the head, mark the wall under it, and measure from the floor to the mark.
2. Chest. Around the fullest part of the chest, under the arms, tape level. Arms down, breathing normally.
3. Waist. Around the natural waistline, the narrowest part of the torso. On a toddler, measure where the waistband of their trousers sits.
4. Inseam. From the crotch to the floor along the inside of the leg, without shoes.
5. Weight, for babies and toddlers. The baby, toddler and kids templates all have a weight row next to height.
6. Write the date next to the numbers. Children grow, and last season's numbers are old.

Kids wriggle. Measure over underwear or thin clothes, take each measurement twice, and keep the larger one.

Age, T sizes and Y sizes

Kids' sizes come in three families, and the same age doesn't always mean the same size. These are the heights on three Ruban Size templates, typical values before a brand puts in its own:

T sizes (2T to 5T) are toddler cuts: the toddler template's note says they leave room for a diaper. Y sizes are kids' cuts. A 4T and a 4Y start at about the same height but don't end at the same one (106 cm against 104 cm), one more reason to shop by height. The Girls' dresses and Boys' trousers templates continue from 4 to 14, with height first on both. Every age side by side is in kids' clothing sizes by age and height.

A worked example

A child of four and a half, 108 cm tall, on the Kids template:

• By age alone: 4Y, for 4 to 5 years. Its heights stop at 104 cm, too short.
• By height: 5Y, 105 to 110 cm, right in the middle.

Find my size answers 5Y and shows both lines: "Height 108 cm: 5Y, middle of the range" and "Age 4.5 years: 5Y, below this size's range". The age only nudges; the height decides.

Common mistakes

• Buying by age alone. Children of the same age aren't the same height, and the label's age assumes a typical one.
• Measuring with shoes on, or with hair up in a bun on top of the head.
• Letting the child slouch or stand on tiptoe. Heels on the floor, back on the wall.
• Measuring over a coat or a thick sweater.
• Keeping old numbers. Measure again before each season.
• Choosing the exact size for something meant to last. Between two sizes, the larger one leaves room to grow; the smaller one is outgrown sooner.

Shoes follow the same logic, by foot length rather than age: see the kids' shoe size chart.

What it means for a Shopify store

Print heights on every kids' chart, not only ages, and say which comes first. Ruban Size's kids templates do: Baby (0-3 M to 18-24 M, height and weight), Toddler (2T to 5T, height, weight and chest), Kids (2Y to 12Y, height, weight and chest), plus Girls' dresses and Boys' trousers (4 to 14, height with chest and waist, or waist and inseam). Each opens as a draft, with typical values you swap for your own.

Add the chest for tops and dresses, the waist and inseam for trousers. The Boys' trousers template's note shows the order for bottoms: "Adjustable waistband inside: choose by height, then by inseam." Here is the toddler template as parents see it:

How Ruban Size handles kids' sizes

On a kids' chart, Find my size speaks to the parent ("Enter your child's measurements. We compare them with this chart.") and asks for what the chart has: height, weight, chest, waist or inseam. When the sizes are ages ("4Y", "2T", "6-12 M"), it adds an Age field, in months for babies.

• Height first. With a height row, height counts most and age is only a hint. Without one, the age carries the answer.
• Room to grow. For children, a size a little too big counts against it less than a size too small, so close calls go to the larger size.
• Kept apart. A child's measurements are saved on the parent's device separately from the parent's own. A parent's chest never fills a child's form, and the child's never replaces the parent's "Your size".
• No estimate for children. The height and weight estimate (on the Fit plan) isn't offered to under 18s, nor on charts that already have a height row.

The guide remembers one child at a time. Shopping for two, type the second child's measurements over the first, or use "Forget my measurements" and start again. Kids sit with rings, shoes, bras and dogs in fit by product type, each type with its own questions.

Questions

Should I buy kids' clothes by age or by height?

By height, then by chest or waist. The age on the label is only a guide: a tall child can wear the next age up.

What is the difference between 4T and 4Y?

4T is a toddler cut and 4Y a kids' cut. On the Ruban Size templates, 4T covers 100 to 106 cm and 4Y 99 to 104 cm, and T sizes leave room for a diaper.

How do I measure my child's height at home?

Barefoot, back and heels against a wall, a book laid flat on the head. Mark the wall under the book and measure from the floor to the mark.

What if my child is between two sizes?

Take the larger one: it leaves room to grow. Find my size leans the same way for children.