One Rep Max Calculator
Estimate your one-rep max from submaximal lifts using the Epley formula
What This Calculator Does
The One Rep Max (1RM) calculator estimates the maximum weight you can lift for a single repetition based on the weight and reps you can perform at a submaximal load. This is useful for programming training percentages without the risk of actually attempting a true one-rep max. The Epley formula used here is one of the most widely accepted methods in strength training.
The Formula
Example Calculations
Example: Bench Press
You bench press 185 lbs for 5 reps. Estimated 1RM = 185 x (1 + 5/30) = 185 x 1.167 = 216 lbs. Your training zones: 90% = 194 lbs, 80% = 173 lbs, 70% = 151 lbs.
Example: Squat
You squat 225 lbs for 8 reps. Estimated 1RM = 225 x (1 + 8/30) = 225 x 1.267 = 285 lbs. Your training zones: 90% = 257 lbs, 80% = 228 lbs, 70% = 200 lbs.
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How to Use Your Results
Use your estimated 1RM to program training weights. For strength, work at 85 to 95 percent of your 1RM for 1 to 5 reps. For muscle growth, use 65 to 80 percent for 8 to 12 reps. For endurance, use 50 to 65 percent for 15 or more reps. Recalculate every 4 to 6 weeks as you get stronger. Never attempt a true 1RM without a spotter.
Frequently Asked Questions
How accurate is the One Rep Max Calculator?
The One Rep Max Calculator uses well-established scientific formulas to provide reliable estimates. The Epley formula is most accurate when using a rep range of 2 to 10 reps. Accuracy decreases with higher rep counts above 10. For precise measurements, consult a healthcare professional or certified personal trainer.
Is the One Rep Max Calculator free to use?
Yes, the Fitnit One Rep Max Calculator is completely free with no sign-up required. Enter your values and get instant results. You can use it as many times as you like.
What formula does the One Rep Max Calculator use?
We use the Epley formula: 1RM = Weight x (1 + Reps/30). Developed by Boyd Epley, this is one of the most commonly used and validated formulas in strength training. It works best with rep ranges of 2 to 10.
How often should I recalculate my estimated 1rm and training percentages?
We recommend recalculating every 4 to 6 weeks, or whenever your weight, activity level, or fitness goals change significantly. Regular updates ensure your targets stay aligned with your current body and lifestyle.
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