Bat Selector
Bat speed, not bat size nor weight, drives the ball. Bat speed is affected by a number of variables including bat length, bat weight, bat Moment of Inertia (MOI) which is often referred to as swing weight or balance point, which are affected by barrel length. Note, a high MOI bat with a given bat weight on a higher swing weight than a lower MOI bat with a heavier bat weight. MOI is more meaningful than bat weight.
One of the hurdles that young hitters especially face is picking the right bat. You must choose a bat that is comfortable and well balanced. The balance of a bat comes from the proportion of weight to length. When you find the correct balance, the result will be a quick, controlled swing!
Length and weight of the right bat should be based on how well you can generate speed in your swing and maintain control. A bat sizing guide based on the hitter’s age, height and weight has been developed as a “starting point”. 
Remember that the balance or MOI of the bat must also be considered on swing feel. Start with the chart to determine estimated length and go up and down from there.
Once you have determined the right length, its time to determine the right weight. A rule of thumb is to try two or three weights (in ounces). One test is to take the handle end of the bat in your right hand if you’re a right-handed hitter (left if you’re a lefty). Point the bat straight out from your side. Keep your arm straight and parallel to the ground. If you can hold the bat like this for about 25 seconds without dropping the barrel, that’s probably the right bat for you.
A bat that is too heavy will result in a slow swing, loss of balance during the swing, loss of optical vision, and poor control of the bat path as you swing at the ball.
If the bat is too light you may not be able to feel the bat head. If you can’t feel where the bat head is, you will suffer a loss of control. In addition, when you swing – your lead shoulder will always open too soon.
When in doubt, “go lighter” which will give you more bat head speed and allow for quicker reaction time.
A chart put together by Terry Bahill and Robert Watts (2000: Keep Your Eye on the Ball) suggests the following formula(s) for determining the optimum weight for a bat.
| Player | Recommended Bat Weight |
| Major League Baseball | Height (in)/3+7 |
| Amateur Baseball | Height (in)/3+6 |
| Junior League Baseball (13-17) | Height (in)/3+1 |
| Little League Baseball (11-12) | Weight (lbs)/18+16 |
| Little League Baseball (9-10) | Height (in)/3+4 |
| Little League Baseball (7-8) | Age x 2+4 |
| Fastpitch Softball | Height (in)/7+20 |
| Slowpitch Softball | Weight (lbs)/115+24 |
Choose your bat based on your physical strength, comfort level and your hand size. The stronger you are the bigger and longer the bat you can handle. NEVER use a bat that feels too heavy or is weighted too much at the end to be comfortable.
In addition to weight of the bat, the balance of the bat or swing weight, often referred to as the Moment of Inertia (MOI) governs how a bat feels and is actually a more meaningful measure of how well it will swing for you. For example, a heavier balanced bat will feel lighter and swing faster than a lighter, end loaded bat. See attached paper [more] about how bat weight, inertia and swing speed are related.
As a general rule, most players can hit a ball further with lighter (really low MOI) bats. It is only the biggest homerun hitters, who can hit the ball further with a heavier (really higher MOI) bats. Also, lighter bats provide more bat control during the swing phase.
Everyone is different when it comes to sizing up for a bat. Use the tables above references only, remembering that there can be other factors that can affect a player’s bat length and weight.
Another important factor in selecting a bat is the Barrel Length. In general, a longer barrel length increases the potential hitting surface and will directly increase good bat and ball contacts and hence batting average. To put it in perspective, the difference between a .281 and .312 hitter (and a Big League million dollar contract and trip to the Hall of Fame) is only one extra hit in 32 at bats. A longer barrel will get you on base more!
To download a copy of our Bat Selector paper [more].