Estimate your 1RM from any rep count. Uses Epley and Brzycki formulas with a full percentage-based training table.
Knowing your one rep max transforms your training from guesswork into a systematic program. Once you have your 1RM, you can prescribe exact weights for every working set based on the percentage required for your goal — strength, hypertrophy, or power. The percentage table in our one rep max calculator shows you exactly what weight to use at each training intensity zone, making it easy to program your workouts with precision. All calculations run entirely in your browser — your data never leaves your device.
Your one rep max (1RM) is the maximum weight you can lift for a single repetition of an exercise with proper form. It is the standard benchmark for measuring absolute strength and serves as the foundation for percentage-based program design across powerlifting, Olympic lifting, and strength conditioning.
Our calculator uses two widely validated estimation formulas:
The calculator averages both formulas to reduce the impact of each formula's individual bias. Results are most accurate when the input set uses 1–10 reps to near-maximal failure. A submaximal approach — testing with a weight you can lift 3–6 times with maximum effort — gives the best balance of accuracy and safety, particularly for pressing movements where a true 1RM attempt without a spotter carries significant risk.
Once your 1RM is estimated, percentage-based training zones make program design precise:
David bench presses 185 lbs for 6 reps with good form, reaching close to failure.
Epley: 1RM = 185 × (1 + 6 ÷ 30) = 185 × 1.2 = 222 lbs
Brzycki: 1RM = 185 ÷ (1.0278 − 0.0278 × 6) = 185 ÷ 0.8610 = 215 lbs
Average estimated 1RM: ∼218 lbs
David can now program his training with precision using percentages of 218 lbs:
Without knowing his 1RM, David would be guessing at weights. With it, every session is systematically tied to his actual strength level — and as his 1RM increases, all training weights scale up proportionally. Retesting every 4–6 weeks (or re-estimating from a top submaximal set) keeps the training weights calibrated to his current capacity.
Rep range used: Both formulas are most accurate when the test set falls between 1 and 10 reps. Above 10 reps, the accuracy of both formulas degrades substantially — particularly Brzycki. A 20-rep set with a light weight will significantly underestimate your true 1RM. For best results, use a weight that limits you to 3–8 reps.
Proximity to failure: The estimation assumes the test set was taken to or near muscular failure. Stopping with several reps left in reserve produces an underestimate. The set should feel genuinely maximal — the last rep should be a real struggle — for the formula to apply correctly.
Fatigue level: Testing after a long workout session or a night of poor sleep artificially reduces performance and therefore underestimates your true 1RM. For the most accurate estimate, perform the test set when fresh — ideally as the first heavy work of a session after a thorough warm-up.
Exercise selection: 1RM estimates are exercise-specific. Your bench press 1RM cannot be used to predict your overhead press 1RM because different movement patterns recruit different muscle groups at different mechanical disadvantages. Estimate separately for each lift you want to program.
Training experience: Novice lifters tend to perform better on higher rep sets relative to their 1RM (they haven't trained the neurological efficiency of true max effort), so their estimates from submaximal sets may be more accurate than true 1RM testing. Advanced lifters are better at expressing maximum force in a single rep, and may find estimated 1RM slightly lower than their true max.
Your one rep max (1RM) is the maximum weight you can lift for a single repetition of an exercise with proper form. It is used as a benchmark for strength and to calculate training weights at different percentages. A 1RM test or estimate is important for programming strength training progressions.
To test your 1RM safely, warm up thoroughly with progressively heavier sets. Use a spotter for pressing movements. Work up in 5–10% increments, resting 3–5 minutes between attempts. Alternatively, use a submaximal rep test (lift a challenging weight for 3–10 reps) and use our 1RM calculator to estimate your max without the risk of a true max effort.
The Epley formula is one of the most widely used 1RM estimation formulas: 1RM = weight × (1 + reps/30). It works best for rep ranges of 1–15 reps. The Brzycki formula (weight ÷ (1.0278 − 0.0278 × reps)) is more accurate for lower rep ranges (under 10 reps). Our calculator shows both and averages them.
Once you know your 1RM, you can program your training at specific intensity percentages. Heavy strength work is typically done at 80–90% of 1RM for 3–5 reps. Hypertrophy (muscle building) training is often at 65–80% for 6–15 reps. Power and speed work uses lighter loads (50–70%). The percentage table in our calculator shows you the target weight for each zone.
Beginners and intermediate lifters can test their 1RM every 4–8 weeks, typically at the end of a training cycle. Advanced lifters may test less frequently — every 8–16 weeks. For everyday training, it is often sufficient to estimate your 1RM from submaximal sets using a calculator like this one rather than doing true 1RM testing regularly.