One Rep Max Calculator
It estimates the heaviest weight you could lift once, from a set you have actually completed, and turns that into a percentage chart for programming your training.
Estimated one-rep max
258.3 lb
Epley
262.5 lb
Brzycki
253.1 lb
Lombardi
264.3 lb
O'Conner
253.1 lb
| % of 1RM | Weight | Approx reps |
|---|---|---|
| 100% | 258.3 lb | 1 |
| 95% | 245.3 lb | 2 |
| 90% | 232.4 lb | 4 |
| 85% | 219.5 lb | 6 |
| 80% | 206.6 lb | 8 |
| 75% | 193.7 lb | 10 |
| 70% | 180.8 lb | 12 |
| 65% | 167.9 lb | 16 |
| 60% | 155.0 lb | 20 |
Broadly: 85–95% for strength, 70–85% for hypertrophy, 50–70% for technique and speed work.
What it calculates
It estimates the heaviest weight you could lift once, from a set you have actually completed, and turns that into a percentage chart for programming your training.
Why it matters
Almost every strength program is written in percentages of your max, but genuinely testing a one-rep max is risky and takes a full session to recover from.
Who it's for
Lifters following a percentage-based program, coaches setting loads, and anyone tracking strength over time.
Formula
- w
- Weight lifted
- r
- Reps completed with good form
- 1RM
- Estimated one-rep maximum
Worked example
100 kg for 5 reps
- 1Epley: 100 × (1 + 5/30) = 116.7
- 2Brzycki: 100 × 36 ÷ (37 − 5) = 112.5
- 3Lombardi: 100 × 5^0.1 = 117.5
- 4O'Conner: 100 × (1 + 0.025 × 5) = 112.5
About 115 kg, averaging the four formulas
How the one rep max calculator works
Each formula extrapolates from the observed relationship between load and reps, and they were fitted on different populations, which is why they disagree by a few percent. Averaging them is more robust than trusting any one. Accuracy is best at low rep counts: a set of three predicts a max far better than a set of fifteen, where the result depends as much on endurance and pain tolerance as on maximal strength.
Each formula extrapolates from the observed relationship between load and reps, and they were fitted on different populations — which is why they disagree by a few percent. Averaging them is more robust than trusting any single one.
Accuracy is best at low rep counts. A set of three predicts a max far better than a set of fifteen, where the result depends as much on endurance and pain tolerance as on maximal strength.
Common mistakes
- Estimating from a set taken well past failure or with degrading form.
- Using sets above ten reps, where every formula loses accuracy quickly.
- Applying a max from one lift to another — deadlift and bench behave differently across rep ranges.
Tips and best practice
- Estimate from sets of three to six reps for the most reliable figure.
- Re-estimate every few weeks rather than testing a true max.
- Leave a rep in reserve when generating the estimate; a grinding set inflates it.
Frequently asked questions
How do I calculate my one-rep max?
Take a set you completed with good form and apply an estimator such as Epley: 1RM = weight × (1 + reps ÷ 30). 100 kg for 5 reps gives about 117 kg.
Which 1RM formula is most accurate?
They perform similarly at low rep counts and diverge above about ten reps. Averaging several — as this calculator does — is more reliable than picking one.
Is it safe to test a true one-rep max?
For experienced lifters with a spotter and a proper warm-up, occasionally. For most people an estimate from a set of three to five carries far less risk for much the same information.
How many reps should I use for the estimate?
Three to six is the sweet spot. Above ten, endurance starts dominating and every formula overestimates.
What percentage of my max should I train at?
Broadly: 85–95% for strength, 70–85% for hypertrophy, and 50–70% for technique and speed work. The chart above converts your estimate into those loads.
Related calculators
Methodology & trust
- Formula source
- Epley, Brzycki, Lombardi and O'Conner one-repetition-maximum equations.
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.