We have all seen it. That one guy at the gym trying to snatch his body weight. When he throws it over its peak he sprains his wrist, drops the weight, and loses a bit of dignity. Whether you are a beginner to getting in shape or a crossfit expert, the number one goal is safety. Using the wrong size weight can lead to injuries both physically and psychologically. You do not want a size too light, nor too heavy.
What factors to consider when choosing your weight? What is your body weight? What is your current fitness level?? What are your workout goals? Have you used kettlebells before? Are you working out by yourself or with a partner? Are you looking to do explosion exercises? Who will be using these kettlebells? How old are you? All these questions should be asked when deciding on the weight and number of kettlebells you should buy.
Now with that said, you obviously want the optimal weight to give you the best workout and push your body. The general suggested weight from most reliable sources say men should start off with a 35lb(16kg) and women should start out with 18lb(8kg). However this does not take into account weight class or experience. Nor does this take into account the primary types of exercises expected to be performed or level of intensity. And if you are like me, I love using multiple sized weights for all my workouts.
Beginning average size males(190lbs) who are newer to fitness or kettlebell exercises should go with a 25lb kettlebell for explosion and higher rep speed and a 35lb kettlebell to really focus on muscle hypertrophy(muscle gains). Again this is not the word of God, so feel free to adjust this to your comfort. Just make sure you have your heart rate up, feel sore after a workout, and are under control of your form during your workout.
Beginning average sized females(150lbs) who are newer to fitness or kettlebell exercises should go with a 12lb kettlebell and a 18lb kettlebell. Females are a bit harder to predict since there tends to be be such a wide variety of body shapes and sizes. The typical female is looking for more muscle tone and cardio workout. If these are your goals, definitely stick to the lower weight ranges that allow to pump out high quantity high quality reps.
Bodybuilders obviously want the higher weight range such as 35lb - 75 lb kettlebells. A great indicator for weight range would be to look at your go to dumbbell weights. And if you are looking to really take your fitness serious you should consider buying 3-5 different weights so you can really push your body in a variety of ranges and speeds.
Elderly or well seasoned kettlebell enthusiasts really want to go on the light side of the spectrum. Assuming your goals are to just keep your muscles healthy and active and you are not planning on entering any Mr. Universe competitions anytime soon. No matter your gender, start on the introduction sizes of 5lb - 15lb kettlebells.
How many should I buy? Ideally you would have a full rack, but unless you are willing to drop a few thousand dollars this isn't going to be the best financial decision for you. I always recommend having at least 2 sizes. One weight should be on the lighter side for higher rep sets, and one should be on the heavier side for low rep sets. This should satisfy the majority of fitness programs and body types out there. Studies have shown that mixing weight size and number of reps can lead to the best muscle growth possible. So you don't want to have just one kettlebell around. Many professional level workout regimens have "hard" days and "easy" days. Having a couple of kettlebell weights laying around help keep your workout consistent. Also keep in mind that if you have a workout partner, make sure neither one of you is compromising for the other just to only to have to buy one kettlebell. These are investments for your future self!
So what is the ultimate answer? Well there is none really. There are a lot of factors to consider. Each person and their goals are different. Just remember to keep form a priority and to start off with just a couple different sizes as you continue to grow.