Calculate child seat size

For an exact determination of the child seat size, the child seat calculator provides the best option for the child's height or weight . Age only plays a subordinate role.

Note : Child seat sizes according to the newer i-Size standard are derived from body size . With the old division into groups , the calculation is based on weight - here, cross-group child seats are ideal for a long period of use.

Child seat size calculator
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Suitable sizes:
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Recommended child seats for this size
Unfortunately, this value is invalid. Please enter a weight between 0 and 36.
Unfortunately, this value is invalid. Please enter a weight between 0 and 12.
Unfortunately, this value is invalid. Please enter a weight between 0 and 150.
Please only enter numbers.

Tip : The compact guide for child seats including current test results is available here.

Standard groups for child seats (size table)

Choosing the right size child seat is a prerequisite for the safety features of a child seat to come into play. There are currently two valid child seat standards : The older UN ECE Reg. 44, which is divided into weight classes 0 to III . And the mentioned newer i-size standard (UN ECE Reg. 129), in which the manufacturers steplessly specify the body size for the correct use (in some cases also with specification of the maximum weight).

Size table for child seat standard groups or phases

Standard groups baby seats
& Child seats		 Weight (approx) Age (approximately) Body size (approx)
i-Size (phase 1) up to 23 kg * Birth up to 4 years 40 cm to 105 cm
i-Size (phase 2) 20 to 36 kg 4 to 12 years 100 to 150 cm
Group 0 up to 10 kg Birth up to 1 year up to 75 cm
Group I. 9 to 18 kg 1 to 4 years 75 cm to 100 cm
Group II 15 to 25 kg ** 3.5 to 7 years up to 125 cm
Group III 25 to 36 kg *** 7 to 12 years up to 150 cm
Child seats that grow with the child
Group 0+ up to 13 kg Birth up to 15 months up to 90 cm
Group 0 + / I up to 18 kg Birth up to 4 years up to 100 cm
Group I / II 9 to 25 kg 1 year to 7 years 72 to 125 cm
Group I / II / III 9 to 36 kg 1 to 12 years 75 to 150 cm
Group II / III 15 to 36 kg 3.5 to 12 years 95 to 150 cm

*: The Isofix anchorage is approved for loads up to 36kg total weight (child plus seat). If the seat is lighter, the children can be heavier.

** Group II seats are rarely offered. Alternative: Group I / II or II / III seats that grow with the child.

*** Group III seats are booster seats without a backrest. Booster seats proved to be inadequate in the crash test. Experts therefore advise against it, as there is no protection in the event of a side impact. Alternative: Group I / II / III or II / III seats that grow with the child.

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