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One Rep Max Calculator

Estimate your one-rep max (1RM) from any weight and rep count using 7 validated formulas. Get your training percentages across all rep ranges — from 50% for warm-up sets to 95% for near-maximal singles — so you can programme your training precisely without ever having to attempt a true max.

Enter your lift details

Enter the weight you lifted and how many reps you completed. For most accurate results use a set of 1–10 reps — estimates become less reliable above 10 reps.

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The load you used for the set
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Best between 1–10 for accuracy
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Used for strength level benchmark

Why estimate instead of test?

True 1RM attempts carry injury risk, require a spotter, and cause significant fatigue. Estimating from a submaximal set is safer, can be done any training day, and is accurate within ±5% for most lifters.

Best rep range for accuracy

1–6 reps gives the most accurate estimate. 7–10 reps is still reliable. Above 10 reps, fatigue affects performance more than strength, making 1RM predictions less reliable.

Tip: for the most reliable estimate, use a weight you can lift for 3–5 reps with good form but not more — stopping 1–2 reps before failure gives the cleanest prediction of your true maximal strength.
1RM estimates are mathematical approximations and vary by individual. Do not attempt a true 1RM without an experienced spotter and adequate warm-up. These figures are for training programme design, not competition preparation.

What is one rep max?

Your one-rep max (1RM) is the maximum weight you can lift for a single full repetition with proper form. It is the gold standard measure of maximal strength for a given exercise and the foundation of percentage-based training programmes used by powerlifters, Olympic weightlifters, and strength athletes.

Rather than testing your 1RM directly — which carries injury risk and requires significant recovery — most lifters estimate it from a submaximal set. If you can lift 225 lb for 5 reps, the formula predicts what a single rep at maximum effort would be.

The 7 formulas explained

Epley (1985): 1RM = w × (1 + r/30) — most widely used, slightly overestimates at high rep counts
Brzycki (1993): 1RM = w × (36 / (37 − r)) — accurate for 2–10 reps, conservative
Lander (1985): 1RM = w / (1.013 − 0.0267123 × r) — good all-round performer
Lombardi (1989): 1RM = w × r^0.10 — tends to give higher estimates
O'Conner et al (1989): 1RM = w × (1 + 0.025 × r) — conservative, good for beginners
Wathan (1994): 1RM = 100w / (48.8 + 53.8 × e^(−0.075 × r)) — non-linear, accurate across rep ranges
McGlothin (1989): 1RM = 100w / (101.3 − 2.67123 × r) — similar to Lander

No single formula is universally superior. The average of all seven gives the most robust estimate. For 1–5 reps, all formulas agree closely. Divergence increases above 8–10 reps as fatigue plays a bigger role.

How to use 1RM for training

50–60% 1RM — Warm-up sets, technique work, very high rep endurance (20+ reps)
60–70% 1RM — Muscular endurance, 15–20 rep sets, metabolic conditioning
70–80% 1RM — Hypertrophy (muscle building), 8–12 rep sets. Primary range for bodybuilding-style training
80–85% 1RM — Strength-hypertrophy, 5–8 reps. Effective for both size and strength
85–92% 1RM — Strength development, 2–5 reps. Powerlifting-style training
92–97% 1RM — Near-maximal singles and doubles. Competition preparation
97–100% 1RM — True 1RM attempts. Requires spotter, adequate warm-up, and fresh state

Strength standards by bodyweight ratio

A common way to assess strength level is the bodyweight ratio — your 1RM divided by your body weight. These are general benchmarks for the squat, bench press, and deadlift for untrained to elite lifters:

Beginner: Squat <1.0× BW · Bench <0.75× BW · Deadlift <1.25× BW
Intermediate: Squat 1.0–1.5× BW · Bench 0.75–1.25× BW · Deadlift 1.25–1.75× BW
Advanced: Squat 1.5–2.0× BW · Bench 1.25–1.75× BW · Deadlift 1.75–2.5× BW
Elite: Squat >2.0× BW · Bench >1.75× BW · Deadlift >2.5× BW

These are broad population benchmarks — they vary by sex, age, body weight category, and training style. They are most useful as directional guidance, not fixed targets.

Frequently asked questions

How accurate is a 1RM calculator?

For sets of 1–6 reps, 1RM formulas are accurate within approximately 2–5% for most lifters. Accuracy decreases for higher rep sets (8+ reps) because fatigue and muscular endurance start to influence performance more than raw strength. Individual response to fatigue also varies significantly between lifters.

Which 1RM formula is most accurate?

Research suggests the Brzycki and Epley formulas perform best for most lifters across 2–10 rep sets. Wathan is considered more accurate for higher rep sets. Using the average of multiple formulas, as this calculator does, gives the most robust and consistent estimate.

Should I test my actual 1RM?

For most recreational lifters, estimated 1RM from a submaximal set is sufficient for programme design and is far safer. True 1RM testing is more appropriate for competitive powerlifters or Olympic weightlifters preparing for competition, and should only be done with an experienced spotter, after an adequate warm-up, and when fully rested.

How often should I recalculate my 1RM?

Every 4–8 weeks is typical for most strength programmes. Many lifters recalculate at the start of each training block. You can also recalculate any time you notice your working weights feel consistently easier than the percentages suggest — a sign your strength has improved.

Can I use this for any exercise?

Yes — the formulas apply to any barbell or dumbbell exercise. They are most validated for compound movements (squat, bench press, deadlift, overhead press). For isolation exercises or machine-based movements, the estimates are still useful but may be slightly less reliable.

Related health calculators

These tools build naturally on your 1RM and strength training goals.

Macro Calculator Set daily protein, carb, and fat targets to support muscle growth alongside your strength training. Lean Body Mass Calculator Estimate your lean mass — useful for setting protein targets and tracking recomposition progress. BMR Calculator Find your base calorie burn to fuel strength training and muscle growth effectively. Calorie Deficit Calculator If fat loss alongside strength training is the goal, set a conservative deficit to preserve muscle.

Disclaimer

One rep max estimates are mathematical approximations based on population-level formulas. Individual results vary based on training experience, muscle fibre composition, fatigue level, and other factors. Do not attempt a true 1RM without a qualified spotter and adequate warm-up. These estimates are for training programme design only and do not constitute professional coaching or medical advice.