Your child grows from left to right. Read straight down from their height to see which seat fits now and what comes next. Dark bars are what we recommend. Light bars are allowed, but less safe.
Two rules, used together. (1) A seat is outgrown when your child reaches either of its limits, height or weight, whichever comes first. (2) A booster is only an option once your child is past both 105 cm and 18 kg. If they outgrow a standard seat on one limit but not the other, move to a bigger rear-facing or harness seat, not a booster. Our recommendation: stay harnessed until 125 cm or 25 kg, whichever comes first. Typical ages are WHO averages; your child may be ahead or behind.