One Rep Max Calculator
Estimate your one-rep max (1RM) for any lift using the Epley, Brzycki, or Lombardi formula.
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The one rep max calculator estimates the maximum weight you can lift for a single rep on any exercise, based on a set you actually performed. Enter the weight you lifted and how many reps you completed — the calculator returns your estimated 1RM using the Epley formula, plus percentage-based training loads for different goals. Knowing your 1RM is fundamental to structured strength training. Most reputable programmes prescribe training loads as a percentage of 1RM — "work at 80% for sets of 5" or "3 × 3 at 90%". Without a reference 1RM, these prescriptions are meaningless. Testing or estimating it lets you load correctly for your current strength level. The calculator also shows percentages immediately useful for programming: 90% for heavy singles and triples, 80% for strength work, 70% for hypertrophy. These three zones cover the majority of barbell training prescriptions. The estimate is most accurate when based on sets of 1–10 reps — accuracy decreases for higher rep sets as fatigue becomes a more significant factor.
How to Use the One Rep Max Calculator
The One Rep Max Calculator is designed to give you an accurate answer in seconds. Follow these steps:
- Step 1: Enter your weight lifted in the Weight Lifted field. The minimum value is 1. The default is 80 kg. Adjust this to match your specific situation.
- Step 2: Enter your reps completed in the Reps Completed field. The valid range is 1 to 30. The default is 5. Adjust this to match your specific situation.
- Step 3: Click Calculate to see your results instantly. The output updates as soon as you submit.
No account or sign-up required. All calculations run locally in your browser — nothing is stored or transmitted to any server.
Example Calculation
Here is what the One Rep Max Calculator produces with its default values. Change any input above to recalculate instantly for your own figures.
Inputs
- Weight Lifted80 kg
- Reps Completed5
Results
- Estimated 1 Rep Max93.3 kg
- 90% of 1RM (heavy work)84.0 kg
- 80% of 1RM (strength)74.7 kg
- 70% of 1RM (hypertrophy)65.3 kg
How It Works
1RM = Weight × (1 + Reps ÷ 30) [Epley Formula]
The Epley formula (1985) is the most widely used 1RM estimation equation in strength and conditioning: Formula: 1RM = Weight × (1 + Reps ÷ 30) Example: 100 kg lifted for 6 reps. 1RM = 100 × (1 + 6 ÷ 30) = 100 × 1.2 = 120 kg From the estimated 1RM, percentage-based loads are calculated by multiplication: 90% (heavy work) = 120 × 0.9 = 108 kg 80% (strength) = 120 × 0.8 = 96 kg 70% (hypertrophy) = 120 × 0.7 = 84 kg The Epley formula tends to slightly overestimate 1RM for higher rep sets (above 10) because the formula assumes a linear relationship between reps and strength that breaks down as sets get longer. For competition or max testing, use the estimate as a starting point and approach actual maxes with progressive warm-up sets rather than attempting the estimate directly. For most training purposes — setting programme loads, comparing progress over time, choosing a starting weight — the Epley estimate is accurate enough.
Frequently Asked Questions
How accurate is a 1RM calculator?
Most 1RM formulas, including Epley, are accurate within 5–10% for sets of 1–10 reps in trained lifters. Accuracy decreases for higher rep sets and varies between individuals based on muscle fibre composition. Use the estimate for programming purposes, not as a number to attempt cold — always work up to near-maximal weights gradually with proper warm-up sets.
What is a good 1 rep max for bench press?
Standards vary by bodyweight and training age. A common benchmark for men: bodyweight is beginner level, 1.25× bodyweight is intermediate, 1.5× is advanced, 2× is elite. For women, the equivalent numbers are roughly 0.75×, 1.0×, 1.25×, and 1.5× bodyweight. These are rough guides — use your own progress over time as the most meaningful benchmark.
What percentage of 1RM should I train at?
Training zones by percentage of 1RM: 55–65% for technical work and warm-ups; 65–75% for hypertrophy (8–15 reps); 75–85% for strength (3–6 reps); 85–95% for maximal strength (1–3 reps); 95%+ for competition maxes. Most programmes rotate through several zones across a training week or cycle for balanced development.
Should I actually test my 1RM or just estimate it?
For beginners and intermediate lifters, estimating from a submaximal set is safer and sufficient for programming. Actual max testing carries more injury risk and requires a longer warm-up and recovery period. Competitive powerlifters and Olympic weightlifters max-test regularly as part of competition. For general fitness goals, estimate from a hard set of 3–5 reps — that range gives the most reliable Epley result.
Is the one rep max calculator free?
Yes — free with no sign-up needed. Enter any weight and rep count to get an instant 1RM estimate and percentage-based training loads. All calculations run in your browser and no data is stored.