Knowing how much weight you can lift is extremely useful when planning your weight-training routines. Different training goals require you to vary your repetition ranges and lift at different percentages of your max. You don't necessarily need to test your max, though, as there are ways you can work out your maximum using a percentage calculation.
It's Not a Guessing Game
Rather than taking a stab in the dark at what you think your max might be, use a formula to work out your estimated maximum. The Brzycki formula, named after its creator Matt Brzycki, is the most common way to predict your one-rep max based off sub-maximal lifting. The left-hand column of the chart gives weight lifted in 5-pound increments, while the top row gives the reps performed. Using this you can scan down the side to find the weight you're using, then scroll across to reference how many reps you can perform at this weight. The corresponding box gives you what percentage of your one-rep max this is. Other commonly used formulas can provide similar results.
Enduring the Higher Reps
When training for muscular endurance you have to work in a higher repetition range. Sets of 12 and above are typically prescribed to build endurance, and you can go as high as 50-rep sets. According to the Dixie State University Fitness Center, training for muscular endurance requires lifting a weight between 40 and 70 percent of your max. For example if your bench press maximum is 200 pounds, perform your sets with 80 to 140 pounds.
A Matter of Muscle
Medium weight and reps are best for muscle gain, notes athletics coach Brian Mackenzie. For optimal growth you need to lift for sets of eight to 12 reps, using 70 to 80 percent of your maximum. If you can perform a max squat of 300 pounds, this means keeping your working sets should be between 210 and 240 pounds for eight to 12 reps.
Go High, Get Strong
To build strength and power you need heavier loads than for endurance and muscle growth. All sets should be six reps or fewer, which means increasing the weight to at least 80 percent of your one-rep max, writes strength coach Charles Poliquin in "Modern Trends in Strength Training." If you're trying to strengthen your deadlift and can lift 300 pounds, all your sets should be at least 240 pounds.