One Rep Max Calculator
Estimate your 1RM from a submaximal set and get a full percentage training table.
About One Rep Max Calculator
One rep max is the gold standard for measuring strength, but testing it directly carries injury risk, especially for beginners. Submaximal testing (lifting a manageable weight for a moderate number of reps) combined with a predictive formula is safer and correlates well with actual 1RM for 1–10 repetitions. The three formulas shown have different mathematical shapes, so their average reduces systematic bias from any single model. Use the resulting 1RM to set training loads: 70–80% for hypertrophy, 80–90% for strength, >90% for maximal strength development.
Formulas
Epley (1985)
1RM = Weight × (1 + Reps/30)
- W
- Weight lifted
- r
- Repetitions completed
Brzycki (1993)
1RM = Weight × 36 / (37 − Reps)
- W
- Weight lifted
- r
- Repetitions completed
Lombardi (1989)
1RM = Weight × Reps^0.1
- W
- Weight lifted
- r
- Repetitions completed
Worked example
With the default values below, One Rep Max Calculator returns Estimated 1RM (average) of 115.6. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Weight Liftedaccepts 1–1,000 kg / lb
- 100 kg / lb
- Repetitions Completedaccepts 1–36
- 5
Results
- Estimated 1RM (average)
- 115.6
- Epley
- 116.7
- Brzycki
- 112.5
- Lombardi
- 117.5
Step by step
- 1Epley= 116.7
- 2Brzycki= 112.5
- 3Lombardi= 117.5
- 4Average 1RM= 115.6
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- 1RM estimates are mathematical predictions, not substitutes for proper progression programming or coaching. Attempting maximum or near-maximum lifts without appropriate training history, technique, and supervision carries injury risk. Always train safely.
- This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
1RM estimates are mathematical predictions, not substitutes for proper progression programming or coaching. Attempting maximum or near-maximum lifts without appropriate training history, technique, and supervision carries injury risk. Always train safely.
Frequently Asked Questions
How many reps should I use for the most accurate estimate?
3–6 reps gives the most accurate prediction. At 1–2 reps the result is almost your actual 1RM. At 10+ reps neural efficiency and muscular endurance become confounding factors, making the estimate less reliable.
Does the unit (kg vs lb) matter?
No — the formula is unit-agnostic. Enter your weight in whatever unit you use and the result will be in the same unit.
Should I attempt my predicted 1RM?
If you're new to heavy lifting, don't. The estimate is a planning tool, not a mandate. Work up to 90–95% of your predicted 1RM for training cycles before testing the actual maximum. Always have a spotter for maximal or near-maximal attempts.