How Wide Should a Kids Bed Be?

Short answer: 90 cm wide and 190 cm long is the standard child's single and it comfortably carries a child to about age 10. From 8–10 upward, 120 × 200 cm is the size that survives sleepovers, growth spurts and the sudden arrival of a friend who is taller than your child. 140 cm is a small double and belongs to teenagers, not to a seven-year-old who still sleeps diagonally.

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The mistake almost everyone makes is buying for the child they have rather than the child they will have in 18 months. Children grow 5–6 cm a year between ages 3 and 12, which means a bed bought for a five-year-old is 40 cm too short by their tenth birthday. The other mistake is the opposite: a 140 cm double for a six-year-old, which eats the wall space the toy storage needed and turns a 3 × 3 m bedroom into a corridor.

Widths and lengths by age

Ninety centimetres is a specific number for a specific reason: it is the width of a standard UK single and it comfortably fits a 180 cm adult, which means it does not need replacing at 12. A 90 cm bed is not a child's bed; it is a bed that happens to be 90 cm wide, and that distinction saves parents €300.

When to move from 90 to 120

Three signals, and any one of them is enough. The child's shoulders are within 12 cm of the bed edges, so there is no room to roll. They ask for a friend to sleep over more than twice a year. Or they turn 10 — because growth does not stop, and a 90 cm bed shared with a friend is a diplomatic incident.

A 120 cm bed is also the size that makes the room useful for a decade: it fits two small people at 10, one teenager at 15, and one adult guest at 20. If the room is 3 × 3 m or bigger, skip the 90 cm altogether and go straight to 120 cm when the child turns 8.

The wall maths

A 90 cm bed leaves 210 cm in a 300 cm room — enough for a 60 cm wardrobe, a 40 cm desk and a 100 cm gap. A 120 cm bed leaves 180 cm — enough for the wardrobe and the gap, not the desk. A 140 cm bed leaves 160 cm, which is wardrobe and nothing else. That is why the 140 cm double so often ends up against a wall with no nightstand, and why the child starts stacking books on the floor.

Vertical space is the answer in small rooms: a 90 cm bed with 60 cm of clearance under it holds three 40 cm storage boxes, which is roughly a chest of drawers' worth of toys. Under-bed storage beats a wider bed in every room under 10 m².

Height off the floor

For a child under 6, mattress top at 40–45 cm means feet reach the floor when sitting, which is the difference between independent and "carry me". For 6–12, 45–50 cm is right. Above that, standard adult heights apply. A bed that is 60 cm to the mattress looks grown-up and is a climbing frame for a four-year-old; if you buy one, put a 40 cm step stool at the side and accept that it will be used as a launchpad.

Bunk and midsleeper caveats

Bunk beds need 75 cm between the lower mattress and the underside of the upper frame, or a child cannot sit up. The top bunk needs a guardrail on every open side, with the gap between rail and mattress no more than 10 cm. Under-6s do not go on a top bunk, full stop, and any bunk with a ladder at the foot end rather than the side is a design failure you will discover at 2 am.

The one purchase that ages well

If you want one bed to last from 8 to 18, buy 120 × 200 cm with a solid slatted base and no built-in drawers. It is wide enough for sleepovers, long enough for a 185 cm teenager, and plain enough that a 15-year-old will not declare war on it. The 200 cm length is the part people skip and the part that matters most — 190 cm is 12 cm of footroom for a 178 cm sleeper, which disappears the moment they inherit their father's height.

Keep reading

More dimension guides are in the collection, and the full index is on the furnolio journal.