Is 85 cm the i-Size version of Group 0+?

No. 85 cm appears on many infant carriers, which is why listings repeat it. Which? also cites 75 cm and 87 cm on named brands. GOV.UK’s Group 0+ figure remains 13 kg. None of those numbers is a published equivalent of the others.

What about nidirect’s “about 83 cm” line?

nidirect uses about 83 cm as an illustration of an early-phase rear-facing i-Size seat up to 15 months. It also says each maker specifies its own height range and maximum weight. Use 83 cm as background, not as your conversion constant.

My baby is 12 kg and 86 cm in a 40–85 cm i-Size carrier. Are they still in Group 0+?

Group 0+ is an R44 weight name. On that i-Size carrier the binding limit is the 85 cm (and any max kg on that label). At 86 cm they are outside this shell’s height range even though 12 kg is under 13 kg.

Can I move up as soon as we reach 9 kg because Group 1 starts there?

GOV.UK’s groups overlap on purpose. RoSPA and Which? both describe staying in the current seat until you hit its upper limit, rather than moving at the bottom of the next group. 9 kg is the start of Group 1, not an order to leave Group 0+.

Guides · Car seats · Group 0+ and i-Size

What is the R44 Group 0+ equivalent i-Size height in cm?

Updated 10 September 2026 · Checked 10 September 2026 · By MayTally research desk — Checked against official UK sources

Is there an official cm twin for Group 0+ (13 kg)?

No. GOV.UK defines Group 0+ as 0 kg to 13 kg, rear-facing baby carrier or rear-facing baby seat with a harness. That is a weight band. It does not publish a matching centimetre figure.

Which? (June 2026) is the consumer line Vinted and Argos listings skip: i-Size infant seats do not share one height group the way R44 shares 13 kg. You read each seat’s measurements. Their examples: many infant carriers 40–85 cm; some Maxi-Cosi carriers stop at 75 cm; some Cybex seats go to 87 cm.

Official records do not say 13 kg = 85 cm. A marketplace “Group 0+ / 40–85 cm” line is two different approval systems printed on one card, not a conversion formula.

What height ranges do infant i-Size seats actually use?

Swipe sideways for the full table

Group 0+ versus typical infant R129 / i-Size ranges — not a conversion
What you are looking at	Typical printed limit	Who states it	What you must still check
R44 Group 0+	0–13 kg, rear-facing	GOV.UK weight table	This child’s weight, and that seat’s own manual
R44 Group 0	0–10 kg	GOV.UK	A narrower weight band — not “almost 0+”
Which? “i-Size baby” review bucket	They group reviews as 40–87 cm (0 to around 15–18 months)	Which? height-groups article, July 2026	A review bucket, not every box
Many infant i-Size carriers	About 40 cm to 75, 85 or 87 cm	Which? too-big article: 75 cm vs 87 cm by brand	The centimetres on this carrier
nidirect “first stage” i-Size note	Rear-facing to 15 months; “up to about 83 cm” as a first-phase illustration	nidirect	Each maker still sets its own height and max weight

GOV.UK groups checked 10 September 2026. Infant height examples from Which? (3 June 2026 and 15 July 2026). nidirect “about 83 cm” is their first-phase illustration, not a UK-wide Group 0+ equivalent. Age columns on shop sites remain a rough guide only.

RoSPA’s types of seat table keeps Group 0+ at 0–13 kg and puts R129 infant seats on a height row (phase 1 towards 105 cm for some toddler seats, rearward-facing to at least 15 months). That is two columns, not an equals sign.

How do I check this infant seat without converting 13 kg?

Read this seat’s label, not the Group 0+ memory If the orange label is ECE R44 Group 0+, the stop number is 13 kg (unless the manual’s head or harness check comes first). If it is R129 / i-Size, copy the centimetre range and any max kg on that same label.
Measure the child the way this label expects Weight for R44. Height for R129 — Which? says lie the baby down and measure crown to heel with legs as straight as possible. Do not use a clothes-shop age chart.
Stop at the first limit this seat prints A long, light baby can hit 85 cm before 13 kg. A shorter, heavier baby can hit 13 kg before 75 cm. Outgrown = first limit on that seat.
Use the manual’s head and harness checks Which?: head higher than the top of the seat is a visual outgrown sign. Rear-facing harness should sit at or just below the shoulders (MKUH NHS leaflet). Those checks can end the seat before either 13 kg or 87 cm.

If height and weight disagree, which limit wins?

The first printed limit on this shell. You do not average 13 kg and 85 cm. You do not keep an R129 carrier in use because the child is “still under Group 0+ weight”. You do not keep an R44 Group 0+ in use because a cousin’s i-Size box said 87 cm.

nidirect’s Regulation 129 section is useful here even when you are comparing systems: as well as the height range, a maximum weight is shown, and “each child restraint manufacturer will specify” both. That is why brand blogs that print “13 kg = 85 cm” are doing the one thing the standards do not.

Why do Vinted and Argos still say Group 0+ next to 40–75 cm?

Because shoppers still search Group 0+. Retailers bolt a familiar weight name onto a height box. Which? is clear that manufacturer height limits vary, and that its own 40–87 cm “i-Size baby” heading is how Which? classifies reviews, not a UN group.

Treat “Group 0+ equivalent” as a search hint. Then ignore it when you set the seat up. The orange label and the manual are the numbers that apply.

In shortIn short: there is no official centimetre twin for 13 kg. Infant i-Size upper heights are usually about 75–87 cm and differ by model. Outgrown means the first limit on that seat — kilos, centimetres, or the head and harness checks — not a 13 kg = 85 cm shortcut.

Questions parents ask

Is 85 cm the i-Size version of Group 0+?: No. 85 cm appears on many infant carriers, which is why listings repeat it. Which? also cites 75 cm and 87 cm on named brands. GOV.UK’s Group 0+ figure remains 13 kg. None of those numbers is a published equivalent of the others.
What about nidirect’s “about 83 cm” line?: nidirect uses about 83 cm as an illustration of an early-phase rear-facing i-Size seat up to 15 months. It also says each maker specifies its own height range and maximum weight. Use 83 cm as background, not as your conversion constant.
My baby is 12 kg and 86 cm in a 40–85 cm i-Size carrier. Are they still in Group 0+?: Group 0+ is an R44 weight name. On that i-Size carrier the binding limit is the 85 cm (and any max kg on that label). At 86 cm they are outside this shell’s height range even though 12 kg is under 13 kg.
Can I move up as soon as we reach 9 kg because Group 1 starts there?: GOV.UK’s groups overlap on purpose. RoSPA and Which? both describe staying in the current seat until you hit its upper limit, rather than moving at the bottom of the next group. 9 kg is the start of Group 1, not an order to leave Group 0+.

Sources

Official pages first. If this page and the official page disagree, the official page wins.

GOV.UK — Child car seats: the rules — checked 10 September 2026
Which? — Five signs your child is too big for their car seat — checked 10 September 2026
Which? — Car seat weight groups and height groups explained — checked 10 September 2026
RoSPA Child Car Seats — Types of seat — checked 10 September 2026
nidirect — Child car seats, restraints and seat belts — checked 10 September 2026
Milton Keynes University Hospital NHS — Car seat information — checked 10 September 2026

This is information, not a guarantee of any payment, and not medical, legal or product-safety advice for your home. Prices and rules change; figures carry the date they were checked. Recall status comes from official records only — a product we cannot find is not a safety all-clear. Tell us if we got a fact wrong.