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1RM Strength Calculator
Calculate your one-rep max for any lift based on your current reps and weight.
The weight you lifted for your set.
Number of reps you completed with good form (1-30).
Select your exercise (for context — the formula works for all lifts).
About This Tool
Your one-rep max (1RM) is the most weight you can lift for a single repetition with proper form. This 1RM calculator uses the Epley formula to estimate your max from any submaximal set, so you never have to risk a true max attempt. Knowing your 1RM is essential for programming strength, hypertrophy, or endurance work. Use our Barbell Plate Loading Calculator to load the exact plates for each percentage.
How to Use
Enter the weight you lifted and how many reps you completed with good form. Select the exercise for reference. The 1RM calculator estimates your max and shows exact weights for common training percentages. Program your working sets — 80% for sets of 8, or 85% for sets of 5-6 — and fuel them with targets from our Protein & Macro Calculator.
FAQ
How accurate is the Epley formula?
The Epley formula is most accurate for rep ranges between 2 and 10. Beyond 10 reps, muscular endurance becomes a bigger factor than pure strength, reducing reliability. For the best estimate, use a weight you can lift for 3-6 reps with solid form. The formula tends to slightly overestimate at higher rep ranges.
Should I actually test my one-rep max in the gym?
For most lifters, there is no need to test a true 1RM regularly. It is fatiguing, carries injury risk, and a submaximal estimate is accurate enough for programming. The NSCA recommends testing only when well-rested with a spotter. Competition powerlifters should test; recreational lifters generally should not.
Why are the weights rounded to 2.5 lbs?
Standard weight plates allow 2.5 lb jumps (a 1.25 lb plate on each side). Rounding gives you a number you can actually load on a barbell. Use our Barbell Plate Loading Calculator to see the exact plate-by-plate breakdown for any weight.
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