it is more correct to compare with the height:
(Unit: CM)
80=12M：Shoulder-to-foot clothing length=63 bust=86 , fits for: 70-80cm height / 9-12 Months

90=18M：Shoulder-to-foot clothing length=67 bust=92 , fits for: 80-90cm height / 12-18 Months

100=24M：Shoulder-to-foot clothing length=70 bust=96 , fits for: 85-95cm height / 18-24 Months

110=3T：Shoulder-to-foot clothing length=72 bust=102 , fits for: 95-105cm height / 3 Years Old

120=4T：Shoulder-to-foot clothing length=74 bust=106 , fits for: 105-115cm height / 4 Years Old

it is more correct to compare with the height:
(Unit: CM)
70=3M/6M：length=56 bust=56 sleeve=25 shoulder=25, fits for: 60-70cm height / 0-6 Months

80=9M/12M：length=64 bust=62 sleeve=28 shoulder=27, fits for: 70-80cm height / 6-12 Months

90=18M：length=68 bust=64 sleeve=31 shoulder=29, fits for: 80-90m height / 18 Months

100=24M：length=72 bust=72 sleeve=33 shoulder=31, fits for: 85-95cm height / 24 Months

110=3T：length=76 bust=76 sleeve=36 shoulder=33, fits for: 95-105cm height / 3 Years Old

120=4T：length=80 bust=80 sleeve=39 shoulder=35, fits for: 105-115cm height / 4 Years Old

it is more correct to compare with the height:
(Unit：CM)
59=3M：full length=49 bust=50 shoulder=22 , fits for: 50-55cm height / 0-3 Months

66=6M：full length=53 bust=52 shoulder=24 , fits for: 55-60cm height / 4-6 Months

73=9M：full length=57 bust=44 shoulder=26 , fits for:60-65cm height / 6-9 Months

80=12M：full length=61 bust=56 shoulder=28 , fits for:65-75cm height / 9-12 Months

90=18M：full length=65 bust=58 shoulder=30 , fits for: 75-85cm height / 12-18 Months

it is more correct to compare with the height:
(Unit：CM)
66/6=3M：full length=49 bust=58 sleeve=22 hips=29, fits for: 59-65m height / 0-3 Months

73/8=6M：full length=53 bust=60 sleeve=24 hips=31, fits for: 65-70m height / 3-6 Months

80/10=9M/12M：full length=57 bust=62 sleeve=26 hips=33, fits for: 70-80cm height / 6-12 Months

90/12=18M：full length=61 bust=64 sleeve=28 hips=36, fits for: 80-90cm height / 12-18 Months

it is more correct to compare with the height:
(Unit：CM)
3M：Hat to toe length=62 Expanded width=78, fits for 0-3 Months

6M：Hat to toe length=70 Expanded width=84, fits for 3-6 Months
Note:
1.There is 2-3% difference according to manual measurement.(1 inch = 2.54 cm)
2.All measurement in cm, please note 1cm=0.3937ch, 1 inch=2.540cm
3.Please check the figures carefully and order the right size, don't completely depend on the " age advice". It's just for reference.