How to Choose the Right Weight for Strength Training

Find your Goldilocks weight—not too heavy, not too light—by following these four rules.

Yes, you should be lifting weights. Strength training can ward off muscle loss, keep your bones strong, increase mobility, and boost overall well-being. The key to maximizing the benefits and staying safe: choosing the right weight for you.

“A fundamental concept of resistance training is progressive overload,” says Jessica Matthews, senior adviser for health and fitness education at the American Council on Exercise. “For your body to adapt, develop strength, and make new gains, you need to keep your body sufficiently challenged.”

When it comes to safety, using a weight that’s either too heavy or too light can compromise your form, Matthews says, which can lead to injuries or aches and pains.

“You want to be like Goldilocks,” says certified trainer Jessica Smith, creator of Walk Strong: 6-Week Total Transformation System. “You need to challenge yourself but not so much that you risk straining your body.”

There’s no exact weight range that works for everyone, so you’ll need to do some experimentation. Here are four rules you can follow to ensure you stay in the safe (and strong) zone.

Rule 1: Start with the Weight You’re Already Carrying

If you’re new to strength training or haven’t done it in a while, Smith suggests starting with just the weight of your body to master exercises with proper form and alignment. “If you’re out of alignment, even two extra pounds creates stress on your joints,” she says. So, before you do squats or lunges with weights, do them without weights. Once you feel good about your form, you can start adding weight.

Rule 2: The Last Few Reps Should Always Be Hard

If you easily finish all your reps and feel like you could’ve done an extra set, the weight is too light. “You want to feel resistance and be challenged during those last few reps,” Smith says. Maybe you could’ve done one or two more reps, but no more than that. However, if you struggle to maintain proper form or can’t finish your set, the weight is too heavy.

It will take a little trial and error to find your sweet spot. It’s better to start light and gradually increase the resistance until it feels challenging. With a weight that’s too heavy, you risk injury or using other muscles to compensate. For example, if you’re using weights that are too heavy during a biceps curl, you may rock your hips or rely on your back muscles to bring the weights up. Both throw your form out of whack.

Rule 3: The Exercise You’re Doing Will Help Determine the Right Weight

The weight you use should correspond to the strength of the muscles you’re working. For example, your glutes are more powerful than your shoulders, so you’ll want a heavier weight for squats than you will for shoulder raises.

“If you’re doing a compound, multi-joint movement such as a squat, you can typically use a heavier weight compared with a more isolated exercise, especially one that targets a smaller muscle group,” Matthews says. This is because the load is distributed across multiple muscles and joints—there are more friends at the party, she says.

If you’re strength training solo, think about the muscles you’re working: smaller muscles, smaller weights. Choose a weight that will be challenging without compromising your form.

If you’re taking a group fitness class, ask the instructor what exercises you’ll be doing that day and to help select your weights. It’s a good idea to grab two or even three sets before the class starts, Smith says. Then you won’t need to stop to track down lighter or heavier weights.

Rule 4: Don’t Shy Away from a Challenge

When you feel ready to increase the weight, it’s safest to go up a pound or two—no more than five. “Gain confidence and keep going, because you have to challenge your body to change it,” Smith says. “We’re all losing muscle mass after age 25, so it’s important to increase or at least maintain muscle to keep doing all the things you want to do as you age.”

That said, listen to your body. If you need to use momentum, feel any pain, or can’t move through the full range of motion, keep experimenting. You haven’t found your Goldilocks weight just yet.

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