Below is a rough guide for bat selection. It is simply a place to start and depends not only on the size of the player but the level of competition (better pitching may require a lighter bat). It is better to err on the light side rather than the heavy side. Today’s power hitters in the major leagues use lighter bats than power hitters of yesterday

Age	Weight Minimum	Weight Maximum	Length Minimum	Length Maximum	Barrel Size
6-7	17 Ounces	19 Ounces	24 Inches	28 Inches	2 ¼
8	19 Ounces	21 Ounces	27 Inches	30 Inches	2 ¼
9	20 Ounces	23 Ounces	28 Inches	30 Inches	2 ¼
10	20 Ounces	23 Ounces	28 Inches	31 Inches	2 ¼
11	21 Ounces	24 Ounces	29 Inches	31 Inches	2 ¼ to 2 5/8
12	23 Ounces	25 Ounces	30 Inches	33 Inches	2 ¼ to 2 ¾
13-14	23 Ounces	28 Ounces	30 Inches	33 Inches	2 ¼ to 2 ¾
15 +	24 Ounces	30 Ounces	30 Inches	34 Inches	2 ¾

Charts can take players' height and weight into consideration which can determine/estimate proper size bat.

While these two factors are important, other characteristics are missing. The bat length, weight, barrel size, grip, brand, and whether the player likes to choke up on the bat are all important factors when determining whether a bat has a good feel in the players hand. Use your best judgement.