1RM Calculator
Estimate your one-rep maximum (1RM) for any lift without actually attempting a max lift. Enter the weight and number of reps you completed to see your estimated 1RM and training percentages using both the Brzycki and Epley formulas.
One-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's the standard measure of absolute strength used in powerlifting, weightlifting, strength training programs, and exercise prescription. Knowing your 1RM enables percentage-based training: most strength programs prescribe workouts as percentages of 1RM (e.g., "work up to 5×5 at 80%" or "5×3 at 85%"), so accurate 1RM estimates are foundational to structured training.
Actually attempting a true 1RM is risky and rarely necessary. A failed max attempt can cause serious injury (a 300 lb squat collapsing on you isn't theoretical), and the neuromuscular fatigue from max testing limits the next several training sessions. The smart alternative: use submaximal performance to estimate 1RM via validated formulas. The Brzycki formula (1RM = Weight × 36 / (37 − Reps)) and Epley formula (1RM = Weight × (1 + 0.0333 × Reps)) are two of the most widely used. Both estimate 1RM accurately within 5-10% for rep ranges of 1-10; accuracy decreases at higher reps where muscular endurance increasingly contributes alongside pure strength.
This calculator computes 1RM estimates using both formulas plus standard training percentages (50-95%). Use it for: tracking strength progression without actual max attempts, programming workout weights based on percentages, knowing what loads correspond to specific rep targets, and comparing performance across exercises. Important caveats: 1RM formulas estimate within ±10% — your actual max may be higher or lower. Compound lifts (squat, deadlift, bench, OHP) follow formulas well. Isolation exercises and lifts limited by technical factors (Olympic lifts) follow formulas less reliably. Athletes should test 1RM periodically (once or twice yearly under safe conditions with spotters) rather than relying entirely on formula estimates.
Inputs
Results
Estimated 1RM
212 lbs
Brzycki Formula
208 lbs
Epley Formula
216 lbs
Training Percentages
| % of 1RM | Weight (lbs) | Approx Reps |
|---|---|---|
| 100 | 212 | 1 |
| 95 | 201 | 2 |
| 90 | 191 | 3-4 |
| 85 | 180 | 5-6 |
| 80 | 170 | 7-8 |
| 75 | 159 | 9-10 |
| 70 | 148 | 11-12 |
| 65 | 138 | 13-15 |
| 60 | 127 | 16-20 |
| 50 | 106 | 20+ |
Formula
How to use this calculator
- Enter the weight you lifted (in pounds).
- Enter the number of clean reps completed (perfect form, full range of motion).
- For most accuracy: use sets in 3-8 rep range, taken to within 1-2 reps of failure.
- Review estimated 1RM from both Brzycki and Epley formulas.
- Review training percentages — use these to plan future workouts at specific intensities.
- For strength programs (Westside, 5/3/1, Starting Strength): use the prescribed % of 1RM to set working weights.
- For hypertrophy programs: train mostly 65-80% (10-15 rep range) using 1RM as reference point.
- Re-test 1RM (actual or formula-based with new performance) every 6-12 weeks to update training percentages.
- Compound lifts (squat, deadlift, bench, OHP) work best with formula estimates. Olympic lifts and isolation exercises follow formulas less reliably.
- For safety: actual 1RM testing should use spotters, safety racks, and proper warm-up. Never max out alone in a commercial gym without spotters.
Worked examples
Tracking strength progression
Lifter does 5×5 at 185 lb bench press in week 1. Brzycki 1RM estimate: 185 × 36 / 32 = 208 lb Training percentages from 208 lb 1RM: Working sets at 80%: 166 lb (round to 165) Hypertrophy sets at 70%: 146 lb (round to 145) Six weeks later, lifter completes 5×5 at 200 lb. New 1RM estimate: 200 × 36 / 32 = 225 lb (+17 lb / +8% in 6 weeks — solid progress for intermediate lifter) New working weights: 80%: 180 lb 70%: 158 lb Periodic re-testing (every 6 weeks or after a training block) keeps percentages calibrated to current strength.
Setting safe 1RM attempt
Lifter recently hit 315 lb × 3 reps on squat. Brzycki 1RM estimate: 315 × 36 / 34 = 333 lb Epley estimate: 315 × 1.1 = 347 lb Average estimate: ~340 lb 1RM. For actual 1RM attempt, smart progression: Warm-up: 135 × 5, 185 × 3, 225 × 1, 275 × 1 (60%, 80%, then opener) Opener: 305 lb (90% — comfortable single, confirms 1RM is realistic) Second attempt: 325 lb (95%, ~3 lb buffer if 333 is real 1RM) Third attempt: 335 lb (target — push for PR within estimate) Don't attempt 350+ unless 335 felt easy. Failed max attempts injure people. Estimate-based programming reduces this risk substantially.
1RM-based percentage program
Lifter's established 1RMs: Squat 405, Bench 285, Deadlift 495, OHP 165. 5/3/1 cycle Week 1 percentages (uses 90% of 1RM as "training max"): Squat training max: 365 Set 1: 65% = 235 × 5 Set 2: 75% = 275 × 5 Set 3: 85% = 310 × 5+ (AMRAP — as many reps as possible) Bench training max: 255 Set 1: 165 × 5 Set 2: 190 × 5 Set 3: 215 × 5+ Programs like 5/3/1 use 1RM-based percentages to systematically progress strength. Without an accurate 1RM, the entire program calibration is off — too light wastes training stimulus, too heavy risks failure and injury.
When to use this calculator
Use this calculator when programming strength workouts using percentages, tracking strength progression over time, estimating safe weights for new exercises, or preparing for an actual 1RM test.
Pair with protein-calculator (recovery support), calories-burned (training energy), and heart-rate-zone (cardio complement to strength training).
Important 1RM considerations:
1. **Most accurate at 1-10 reps.** Formulas are calibrated for moderate rep ranges. Estimates at 15+ reps are unreliable because muscular endurance increasingly contributes (different physiological system than pure strength).
2. **Stop reps 1-2 short of failure.** True-failure reps reduce future training capacity and don't improve formula accuracy. Estimate from a set taken to 1-2 reps shy of failure for best practice.
3. **Compound lifts predict better than isolation.** Squat, deadlift, bench, OHP, row follow formulas well. Biceps curl, lateral raise, calf raise follow less reliably (smaller muscles, different fatigue dynamics).
4. **Olympic lifts don't follow formulas well.** Clean, snatch, jerk are technique-limited as much as strength-limited. Formula estimates are rough at best. Olympic lifters should test actual max periodically.
5. **Test actual 1RM safely and periodically.** Once or twice yearly with proper warm-up, spotters, and safety equipment. Confirms formula calibration and provides true reference points.
6. **Brzycki vs. Epley.** Brzycki slightly more conservative (lower 1RM estimate at higher reps). Epley slightly more aggressive. Both within 5% in 1-5 rep range. Use either or average them.
7. **Training percentages vary by exercise.** Same 80% feels different on deadlift (CNS-intensive, ~5 reps max) vs. squat (~6 reps max) vs. bench press (~6-7 reps max). Adjust expectations based on exercise.
8. **Beginners progress fast; advanced slowly.** Beginning lifters add 5-10 lb to major lifts weekly. Intermediate: 5-10 lb monthly. Advanced: 5-10 lb every 2-3 months on a working set. Recalibrate 1RM accordingly.
9. **Training intensity guidelines (percentages):** - Endurance (15-20+ reps): 50-65% - Hypertrophy (6-12 reps): 65-85% - Strength (3-6 reps): 80-90% - Power/Maximum (1-3 reps): 90-100%
10. **Sleep, nutrition, and stress affect performance.** Same lifter can have 5-10% lower performance on a bad day. Don't mistake one-off underperformance for true strength loss.
11. **Equipment matters.** Belt, knee sleeves, wraps, and lifting straps can add 5-15% to max lifts. Be consistent about equipment when comparing estimates over time.
12. **Form must match across estimates.** Comparing 5RM with form A to 1RM with form B is invalid. Maintain consistent depth, tempo, and technique for valid progression tracking.
Common mistakes to avoid
- Using formula estimates for sets above 10 reps. Accuracy drops substantially in higher rep ranges where endurance dominates.
- Attempting 1RM without proper safety setup. Failed max attempts cause serious injuries. Use spotters and safety racks.
- Comparing 1RM estimates across different forms or equipment. Belt/sleeves/wraps add 5-15%; same lift, different setup isn't apples-to-apples.
- Not re-testing 1RM. Strength changes over training cycles. Outdated 1RM means outdated programming percentages.
- Trusting one-day performance. Bad sleep, stress, or under-fueling can drop performance 5-10%. Don't mistake this for true strength change.
- Applying formulas to Olympic lifts. Technique-limited movements don't follow strength formulas reliably. Test actuals.
Frequently Asked Questions
Sources & further reading
- Strength Training Guidelines — American College of Sports Medicine
- Powerlifting Resources — International Powerlifting Federation
- Strength & Conditioning Research — National Strength and Conditioning Association