Below is as height/weight chart for Standard Jerseys, it's based more on the modern Isle & Danish Jersey and stated that American Jerseys may be larger than the chart.
Age (Months)---------Weight (Pounds)--------Height (Inches)
1......................................................93 - 108..............................22 - 29
2....................................................122 - 146..............................30 - 33
3....................................................155 - 177..............................32 - 34
4....................................................183 - 217..............................34 - 36
5....................................................233 - 278............................35 - 38
6....................................................259 - 321.............................36 - 38.5
7....................................................303 - 362............................38 - 40
8....................................................335 - 412.............................39 - 41
9....................................................373 - 436............................39.5 - 41.5
10...................................................391 - 483............................40 - 42
11....................................................428- 499.............................41 - 43
12...................................................471 - 548............................42 - 44
13...................................................500 - 571............................42.5 - 44.5
14...................................................535 - 602...........................44 - 45
15...................................................565 - 640...........................44.3 - 46
16...................................................583 - 661............................44.6 - 46.3
17...................................................609 - 696...........................45 - 46.6
18...................................................639 - 753...........................45.3 - 47
19...................................................651 - 769............................45.6 - 47.3
20..................................................698 - 813.............................46 - 47.6
21...................................................719 - 827............................46.5 - 48
22..................................................758 - 860............................47 - 49
23..................................................760 - 878............................47.5 - 49.3
24..................................................790 - 893............................48 - 49.6