One Rep Max Calculator

Your one rep max (1RM) — also called 1-rep max, max lift, or simply your max — is the heaviest weight you can lift for a single repetition of an exercise with perfect form. It is the universal currency of strength training: powerlifters compete with their 1RMs in squat, bench, and deadlift, and most strength programs prescribe loads as a percentage of 1RM (e.g. "5 × 5 at 80%"). This 1RM calculator estimates your max from any working set so you don't have to actually attempt a true maximum, which is more stressful and carries higher injury risk.

1RM is estimated using validated formulas that relate the weight × reps you completed to your projected maximum single. The two most cited are Brzycki: 1RM = w × 36 ÷ (37 − r) and Epley: 1RM = w × (1 + 0.0333r), where w is the weight lifted and r is the reps completed. Our one rep max calculator runs six different formulas (Brzycki, Epley, Lander, Mayhew, O'Conner, Wathan) and averages them, which research shows produces the most robust prediction across different rep ranges and lifter populations.

No single formula wins universally. Brzycki is most accurate at 1-10 reps and tends to under-predict above 10. Epley is slightly more generous and stays accurate up to ~12 reps. Lander is similar to Brzycki. Mayhew and Wathan use exponential decay and behave better at higher reps. Studies comparing them generally find error of ±5-10% from actual 1RM when the working set is performed to true failure at 3-8 reps. For programming purposes the average of all six is more than accurate enough.

For best accuracy use a working set at 3-8 reps to true failure (RPE 9-10) or 1 rep shy of failure. At 1-2 reps the formula adds little information beyond the weight you actually lifted; at 12+ reps the prediction error grows because muscular endurance, breathing pattern, and form fatigue start to dominate. The sweet spot is 5 reps — short enough for high accuracy, long enough to be sustainable as a regular working set.

True 1RM attempts carry higher injury risk than sub-maximal work because the load is at the limit of your structural capacity and small form breakdowns become serious. They are also more taxing on the central nervous system and require longer recovery. Most strength coaches recommend using a formula-based estimate from a 3-5 rep working set for programming, and only attempting a true 1RM at the peak of a planned strength cycle, after a proper warm-up progression, in a safe environment with a spotter or safety bars. Beginners should never attempt a true 1RM until they have at least 6-12 months of consistent training and good form.

Strength standards vary by bodyweight, age, sex, and training experience. As a rough guide for an 80 kg / 175 lb adult male: Novice — bench 60 kg, squat 80 kg, deadlift 100 kg. Intermediate — bench 90 kg, squat 130 kg, deadlift 160 kg. Advanced — bench 130 kg, squat 180 kg, deadlift 220 kg. Elite — bench 165 kg+, squat 230 kg+, deadlift 270 kg+. Women's standards are typically 65-75% of these figures. ExRx and Strength Level provide detailed standards by bodyweight class if you want a finer comparison.

Most strength programs prescribe loads as a percentage of 1RM. Typical zones: 85-100% (1-5 reps) max strength and neural adaptation; 70-85% (4-8 reps) strength and power; 60-75% (8-12 reps) hypertrophy / muscle growth; 50-65% (12-20 reps) muscular endurance; 30-50% warm-up sets and speed work. A balanced program rotates through multiple zones over a periodised cycle. Use the % table in this calculator to find the exact load you need for any prescribed set.

Estimated 1RM assumes an average strength-endurance profile. Powerlifters who train heavily in the 1-5 rep range often hit a higher actual 1RM than the formula predicts, because they've trained their nervous system to recruit more motor units at near-maximum loads. Bodybuilders and endurance athletes who train mostly at 8+ reps often hit a lower actual 1RM than the formula predicts, because they've trained for endurance, not maximum recruitment. Use the estimate as a starting point and verify on the platform.

Beginners can re-test every 4-6 weeks while gains are fast. Intermediate lifters every 8-12 weeks. Advanced lifters every 12-16 weeks or at the end of each training block. Avoid testing too frequently — true 1RMs are stressful and slow recovery for several days. Most coaches recommend tracking working-set performance week to week and only formally retesting 1RM at the conclusion of a planned cycle.

Yes. The 1RM formulas are mechanism-agnostic — they work for any resistance lift: barbell, dumbbell, kettlebell, machine, or band. Just enter the total weight you lifted (for dumbbells, that's the per-dumbbell weight, not combined). Note that dumbbell 1RM is typically 5-15% lower than barbell because of the extra stabilisation demand, and machine 1RM is typically 5-20% higher because the resistance path is fixed. Cross-comparing 1RMs across modalities is misleading — use the calculator to track each lift's progression separately.

For weighted bodyweight exercises (weighted pull-ups, dips, etc.) — yes. Enter your bodyweight + added load as "weight lifted" and the reps you completed. For pure bodyweight exercises with no added load, the concept of 1RM doesn't apply in the same way; progression is measured in maximum unbroken reps rather than max load. Tools like RTS-style rep maxes (1RM, 3RM, 5RM, 10RM) become a more useful framework for bodyweight progression.

For most healthy lifters using a 3-8 rep working set performed to true failure, 1RM estimation formulas are accurate within ±5-10% of the actual one-rep maximum. Accuracy drops at very high rep ranges (12+) and for highly trained powerlifters whose strength-endurance ratio sits outside the average. For training purposes — picking loads, tracking progress, planning a peaking cycle — the estimate is more than accurate enough. For competitive maxing, peak the cycle, work up properly, and verify the actual number on the platform.