One Rep Max Calculator
Enter the weight you lifted and how many reps you did and get your estimated one rep max plus a full percentage breakdown for programming your training.
Your one rep max is the foundation of smart strength training. Every percentage-based program — 5/3/1, Westside, linear progression — runs off this number. Testing your true 1RM is risky and exhausting. This calculator estimates it from a set you already did so you can program your training without maxing out every week.
Your Lift
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Enter your lift and click Calculate
Your 1RM estimate and percentage table will appear here
How to Use It
Step 1 — Enter the weight you lifted
Use the actual weight on the bar including plates. Toggle between lbs and kg depending on how you train.
Step 2 — Enter your rep count
Use a set where you left one or two reps in the tank. The closer to failure you were, the more accurate the estimate. Sets of 1 to 10 reps give the best results.
Step 3 — Read your 1RM
Your estimated max shows instantly. The percentage table below it gives you the training weights for every intensity zone.
Step 4 — Use the table to program your training
Pick the percentage your program calls for and use that weight. No more doing math in the gym.
How the Math Works
This calculator uses the Epley formula, the most widely used 1RM estimation method in strength and conditioning: 1RM = Weight × (1 + Reps / 30).
Example: You lift 225 lbs for 8 reps. 1RM = 225 × (1 + 8/30) = 225 × 1.267 = 285 lbs.
The Epley formula is most accurate for sets between 1 and 10 reps. Beyond 10 reps the estimate becomes less reliable because muscular endurance starts playing a bigger role than pure strength.
Who This Is For
Powerlifters and strength athletes who program by percentage
Gym-goers running structured programs like 5/3/1, Starting Strength, or GZCLP
Coaches programming training loads for athletes
Anyone who wants to know their max without the risk of actually maxing out
Tips for Using Your 1RM
Use a near-failure set for accuracy
The formula works best when you're close to your limit. A set where you had five reps left in the tank will underestimate your max. Use a set of 3 to 5 reps at a weight that genuinely challenges you.
Stick to 10 reps or fewer
The Epley formula loses accuracy above 10 reps. If you want a good estimate, use a heavy set in the 3 to 8 rep range.
Recalculate every 4 to 6 weeks
Your strength changes. If you're on a progressive program, recalculate your 1RM every training block so your percentages stay accurate.
Don't use your 1RM to ego lift
Your estimated max is a programming tool, not a challenge. Use the percentage table to train smarter, not to load the bar to your max every session.
Different lifts, different maxes
Run the calculator separately for each lift. Your squat max, bench max, and deadlift max are all different numbers and need to be tracked independently.
Your 1RM will vary day to day
Sleep, nutrition, stress, and fatigue all affect your strength on a given day. Treat your estimated max as a baseline, not a hard ceiling.