It is correct to compare the height:
(Unit: cm)
80 = 9 months - 12 months: length = 50 shoulder = 20 chest = 53 waist = 51, fits: 70-80 centimeters height / 9-12 months

90 = 18 M-24 M: length = 55 shoulder = 21 chest = 57 waist = 55, fits: 80-90 centimeters height / 18-24 months

100 = 3t: length = 60 shoulder = 23 chest = 61 waist = 59, fits: 90-100 centimeters height/3 years

110 = 4T: length = 65 shoulder = 24 chest = 65 waist = 63, fits: 100-110 centimeters height / 4 years old

120 = 5T: length = 70 shoulder = 26 chest = 69 waist = 67, fits: 110-120 centimeters height / 5 years old

130 = 6T: length = 75 shoulder = 27 bust = 73 waist = 71, fits: 120-125 centimeters height/6 years
Note:
1. There is a 2-3% difference according to manual measurement. (1 inch = 2.54 centimeters)
2. All measurements are in cm, please note 1 centimeter = 0.3937 inches, 1 inch = 2.540 centimeters.
3. Please check the numbers carefully and request the appropriate size; do not rely entirely on the 'age advice.' It is only for reference.