How accurate are these formulas?

Within ± 5% of laboratory-tested 1RM at 2-10 reps in trained lifters (LeSuer 1997). Accuracy declines at higher rep counts and in untrained lifters.

Should I actually test my 1RM?

Only with a spotter, adequate warm-up, and prior training experience above 80% 1RM. For most lifters, a well-executed set of 3-5 reps yields a more useful estimate than a true attempt.

Which formula should I trust?

Both. Their average is a reasonable central estimate; the gap between them tells you how uncertain the estimate is (usually 2-3% at low reps, widening at higher reps).

Does this work for bodyweight exercises?

Not directly — 1RM formulas assume progressive external load. For bodyweight movements, tempo, range of motion and added weight (vest, plate) are better progression variables.

Where do my numbers go?

Nowhere. Every value stays on your device.

Fitness · Strength training

One-Rep Max (1RM) Estimator Calculator

Epley + Brzycki 1RM prediction with NSCA %1RM training-zone loads.

Your details

Weight lifted

Weight liftedThe load you completed with clean form.

Reps completedPrediction accuracy is best at 2-10 reps; degrades beyond 12.

reps

Estimates are most accurate at 2-10 reps. Never test a true 1RM without a spotter, adequate warm-up, and appropriate strength-training experience.

Estimated 1RM

68.8

< 4≥ 13

Strength zone

A set of 4-6 reps sits in the classic strength zone (~85-90% 1RM). This is the sweet spot for strength gains with a reasonable margin of safety — and 1RM prediction is very reliable in this range.

Both formulas side-by-side

Epley 1985

70 kg

Brzycki 1993

67.5 kg

Your set was approximately

87% of 1RM

Suggested working-set loads (from your estimated 1RM)

60% · 12-20 reps

Endurance / technique

41.5 kg

70% · 10-15 reps

Hypertrophy (lighter)

48 kg

75% · 8-12 reps

Hypertrophy

51.5 kg

80% · 6-10 reps

Hypertrophy / strength

55 kg

85% · 4-6 reps

Strength

58.5 kg

90% · 2-4 reps

Strength / power

62 kg

95% · 1-2 reps

Peak strength

65.5 kg

%1RM zones from NSCA Essentials of Strength Training (4th ed., 2016). Never test true 1RM without a spotter, adequate warm-up, and prior experience at 85% + loads.

Epley vs. Brzycki — why show both?

The Epley (1985) formula is linear in reps and slightly OVER-estimates 1RM at higher rep counts; the Brzycki (1993) formula is non-linear and tends to under-estimate at very high reps. LeSuer 1997 showed both are within ±5% of true 1RM at 2-10 reps in trained lifters — averaging them is a common, defensible approach.

What %1RM to train at

For strength: 3-5 sets of 4-6 reps at ~85% 1RM. For hypertrophy: 3-4 sets of 8-12 at ~70-75% 1RM. For muscular endurance: 2-3 sets of 15+ at < 65% 1RM. Most programmes rotate between these ranges every 4-8 weeks (block periodisation).

When NOT to test a true 1RM

True 1RM testing carries meaningful injury risk without a spotter, technique coaching at load, adequate warm-up, and prior experience at 85-95% loads. For most lifters, an estimate from a well-executed set of 3-5 reps is more useful and safer than a true attempt.

Form before load — always

A 5-rep set at moderate load with clean form gives a more reliable 1RM estimate than a heavier set with breakdown. If technique fails, the estimate is meaningless. Video review of one set per session is a cheap upgrade.

Category reference

Category	Range	What it means
Peak strength	1-3 reps	~ 90-100% 1RM. Neural adaptation. Highly accurate prediction.
Strength	4-6 reps	~ 85-90% 1RM. Sweet spot for strength with reasonable safety margin.
Hypertrophy	7-12 reps	~ 65-80% 1RM. Classic muscle-growth zone.
Muscular endurance	13+ reps	< 65% 1RM. Prediction becomes less reliable here.

Limitations & caveats

Accuracy is best at 2-10 reps; degrades beyond 12.
Assumes clean form on every rep — a broken set gives an unreliable estimate.
Different exercises give different 1RM predictions — do not extrapolate between lifts.
Beginners and detrained lifters may see 1RM change faster than the formulas predict.

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Frequently asked questions

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Clinical Interpretation

Strength zoneNormal

A set of 4-6 reps sits in the classic strength zone (~85-90% 1RM). This is the sweet spot for strength gains with a reasonable margin of safety — and 1RM prediction is very reliable in this range.

Common causes

•Standard strength-block programming

Lifestyle considerations

•3-5 sets of 4-6 at ~85% 1RM is a well-studied prescription for strength
•Rest 3-5 min between sets
•Track loads across weeks — small progressive overload compounds fast

When to consult a healthcare professional

No specific action based on rep range.

Medical Evidence

How we ground the One-Rep Max (1RM) Estimator

Grade A · Clinical guidelines & meta-analysesLast reviewed Feb 12, 2026

Named clinical guidelines

Epley B (1985) — Poundage Chart, Boyd Epley Workout, Univ. of Nebraska.
Brzycki M (1993) — Strength Testing, JOPERD 64(1):88-90.
LeSuer DA et al. (1997) — Accuracy of prediction equations for the 1RM bench press, squat, deadlift — J Strength Cond Res.
NSCA Essentials of Strength Training and Conditioning, 4th ed. (2016) — %1RM training zones.

References

LeSuer et al. — Accuracy of 1RM prediction equations· J Strength Cond Res 1997
NSCA — Essentials of Strength Training and Conditioning· National Strength and Conditioning Association

One-Rep Max (1RM) Estimator Calculator

Your details

Epley vs. Brzycki — why show both?

What %1RM to train at

When NOT to test a true 1RM

Form before load — always

Category reference

Limitations & caveats

Frequently asked questions

How accurate are these formulas?

Should I actually test my 1RM?

Which formula should I trust?

Does this work for bodyweight exercises?

Where do my numbers go?

Keep exploring

Target Heart Rate Zones

VO₂ Max Estimator

BMI Calculator

Read up on the science

Creatinine and eGFR: What These Kidney Function Results Mean Together

BUN Blood Test Explained: What High and Low Results Can Mean

Urine Albumin-to-Creatinine Ratio: An Early Kidney-Damage Test Explained

Cystatin C Blood Test: When It Adds Useful Information Beyond Creatinine

Strength zoneNormal

How we ground the One-Rep Max (1RM) Estimator