Free 1RM Calculator
Epley + Brzycki Formula
Estimate your one-rep max from any set — then see every training percentage from 70% to 95% instantly.
Calculate Your 1RM
What Is a One-Rep Max (1RM)?
Your one-rep max is the maximum weight you can lift for a single complete repetition with proper form. It's the foundational number in strength training — every percentage-based program (5/3/1, Texas Method, nSuns, GZCLP) derives its working weights from your 1RM.
Testing your true 1RM by maxing out is occasionally useful but comes with fatigue and injury risk. Most lifters use an estimated 1RM (e1RM) calculated from a submaximal set — for example, the weight you lifted for 5 reps.
The Epley Formula
Developed by Boyd Epley in 1985, this is the most widely used 1RM estimation formula:
1RM = Weight × (1 + Reps / 30)
Epley's formula performs best in the 1–10 rep range. It slightly overestimates at very high rep counts (15+) but remains the industry standard for strength tracking software.
The Brzycki Formula
Matt Brzycki's 1993 formula uses a different approach:
1RM = Weight × (36 / (37 - Reps))
Brzycki tends to give slightly lower estimates than Epley for sets of 5–8 reps. The two formulas converge near 1 rep and diverge as reps increase. LiftLog displays both so you can see the range and choose whichever aligns with your actual strength.
Training Percentages: What Each Zone Does
Once you have an e1RM, every percentage zone has a specific training purpose:
| Zone | % 1RM | Rep Range | Primary Adaptation |
|---|---|---|---|
| Maximal Strength | 90–100% | 1–3 | Neural drive, peak force |
| Strength | 85–90% | 3–5 | Strength + some hypertrophy |
| Hypertrophy / Strength | 80–85% | 5–8 | Size + strength crossover |
| Hypertrophy | 75–80% | 8–12 | Muscle growth |
| Endurance / Volume | 65–75% | 12–20 | Metabolic conditioning |
Why Progressive Overload Requires Accurate 1RM Tracking
Progressive overload — systematically increasing the stress placed on muscle over time — is the single most important driver of strength and size gains. Without tracking, you can't measure overload. Without an accurate e1RM, you can't program it.
When your 1RM goes up, your training percentages go up with it. A 5/3/1 Week 1 set at 65% feels different on a 300 lb squat vs a 330 lb squat. Re-testing and updating your training maxes every 4–6 weeks is standard practice in all percentage-based programs.
LiftLog tracks your e1RM automatically from every logged set. When you hit a new record, you get an immediate notification. Your progression chart shows the full history. No manual calculations, no spreadsheets.
How Does My 1RM Compare to Other Lifters?
Once you have an estimated 1RM, the natural next question is: where does it rank? Use the Strength Standards Calculator to see your tier (Untrained through Elite) and your approximate percentile rank among lifters at your bodyweight. It also shows you exactly how many pounds you need to reach the next level — which makes a useful programming target.
Limitations of 1RM Estimation
Estimated 1RMs are useful benchmarks, not exact science. Several factors affect accuracy:
- Rep range: Formulas are most accurate between 2–10 reps. A 20-rep set with light weight will overestimate.
- Individual variation: Fast-twitch dominant lifters tend to overperform at low reps; slow-twitch lifters may outperform the formula at higher reps.
- Form breakdown: If reps 4 and 5 were grinders with form degradation, your e1RM is inflated.
- Fatigue: End-of-workout sets give lower estimates than fresh openers.
Use e1RM for programming and trend tracking, not absolute comparison between individuals.