One Rep Max Calculator
Estimate your one-rep max from any set using the Epley, Brzycki, Lombardi and O'Conner formulas, and get a percentage table for programming 1–12 rep sets.
One Rep Max Calculator: with the default inputs, 1rm (epley) is 262.5 lb.
A set taken to (or within a rep of) failure. Estimates are most accurate for 2–10 reps.
- Brzycki
- 253.1 lb
- Lombardi
- 264.3 lb
- O'Conner
- 253.1 lb
- Average of the four
- 258.3 lb
Assumptions
- Epley is the headline; at 1 rep all formulas return the weight lifted.
- The set is assumed to have been taken to or near failure with consistent form.
- Percentage table uses NSCA values; individual rep-max relationships vary by exercise and training history.
| Reps | % of 1RM | Load(lb) | Load (Epley curve)(lb) |
|---|---|---|---|
| 1 | 100% | 262.5 lb | 254 lb |
| 2 | 95% | 249.4 lb | 246.1 lb |
| 3 | 93% | 244.1 lb | 238.6 lb |
| 4 | 90% | 236.3 lb | 231.6 lb |
| 5 | 87% | 228.4 lb | 225 lb |
| 6 | 85% | 223.1 lb | 218.8 lb |
| 7 | 83% | 217.9 lb | 212.8 lb |
| 8 | 80% | 210 lb | 207.2 lb |
| 9 | 77% | 202.1 lb | 201.9 lb |
| 10 | 75% | 196.9 lb | 196.9 lb |
| 11 | 70% | 183.8 lb | 192.1 lb |
| 12 | 67% | 175.9 lb | 187.5 lb |
Percentages from the NSCA's training-load chart (Essentials of Strength Training and Conditioning). The Epley-curve column inverts the formula instead; the two agree within a few percent up to 10 reps.
How this is worked out
The formula
Epley (1985): 1RM = w × (1 + r ÷ 30) Brzycki (1993): 1RM = w × 36 ÷ (37 − r) Lombardi (1989): 1RM = w × r^0.10 O'Conner (1989): 1RM = w × (1 + r ÷ 40) w = weight lifted, r = reps completed
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Weight lifted
- A number.in lb, kg · from 1 to 2000 · defaults to 225
- Reps completed
- A set taken to (or within a rep of) failure. Estimates are most accurate for 2–10 reps.from 1 to 30 · whole numbers only · defaults to 5
What you get back
- 1RM (Epley)main answer
- Brzycki
- Lombardi
- O'Conner
- Average of the four
What this assumes
- Epley is the headline; at 1 rep all formulas return the weight lifted.
- The set is assumed to have been taken to or near failure with consistent form.
- Percentage table uses NSCA values; individual rep-max relationships vary by exercise and training history.
About this calculator
Your one-rep max is the heaviest weight you can lift once with good form. It's the reference point most strength programs are written against — "5 × 5 at 80%" means nothing without it — but actually testing it is fatiguing, slightly risky, and something most people should do rarely. A submaximal set of 3–8 reps plus a prediction formula gets you within a few percent, safely.
The formulas
Every equation here was fitted to real lifters' data, and they disagree in predictable ways:
- Epley is the most widely used and the default here. It's linear — each extra rep adds 3.3% — which slightly overestimates at high reps.
- Brzycki is nearly identical to Epley up to about 10 reps and then climbs faster; at 36 reps it goes to infinity, a reminder that these are curve-fits, not physiology.
- Lombardi uses a power law and is the most conservative at moderate reps.
- O'Conner is Epley with a gentler slope (2.5% per rep), so it reads lowest at 5–10 reps.
LeSuer and colleagues' 1997 comparison found Epley and Brzycki-type equations most accurate for the bench press, with all formulas under-predicting the squat and deadlift by a few percent. Take the average if you want a hedge; take Epley if you want the number everyone else uses.
How to get a good estimate
- Use a set where the last rep was genuinely hard — true failure or one rep short.
- Keep reps between 2 and 10. Accuracy falls off sharply beyond that; a 15-rep set is a test of endurance, not strength.
- Use the same exercise. A 5-rep max on leg press says nothing about your squat.
- Expect the estimate to run a little low on deadlifts and squats and a little high on isolation exercises.
Using the percentage table
The table converts your estimated max into training loads. It uses the NSCA's rep-max chart — the one in most strength-coaching textbooks — alongside the inverted Epley curve so you can see where they differ. Load for 5 reps at 87% is a solid default; move to the Epley column if your reps-in-reserve feel off.
Limits
Rep-max relationships vary by exercise (upper body tolerates more reps per percentage than lower body), by training history (endurance-trained lifters get more reps at a given percentage) and by day. Treat the estimate as ±5%, retest with a different rep range if it seems off, and let bar speed and reps-in-reserve override the arithmetic.
Frequently asked questions
▸How do I calculate my one rep max?
Lift a weight for as many clean reps as you can (ideally 2–10), then apply Epley: weight × (1 + reps ÷ 30). For 225 lb × 5, that's 225 × 1.167 ≈ 262 lb.
▸Which 1RM formula is most accurate?
Epley and Brzycki perform best in comparisons, especially for the bench press, and are almost identical up to 10 reps. All formulas underestimate squats and deadlifts slightly.
▸How many reps should I use to estimate 1RM?
Between 2 and 10, with 3–5 the sweet spot. Beyond 10 reps the formulas diverge and the estimate becomes unreliable.
▸Is it safe to test a true 1RM?
For experienced lifters with a spotter or safeties, yes, occasionally. Beginners gain nothing from it — a 3–5 rep test plus a formula is safer and nearly as accurate.
▸What percentage of 1RM should I train at?
Strength: 80–90% for 2–6 reps. Hypertrophy: 65–80% for 6–12. Power: 30–60% moved fast. The table shows your loads at each percentage.
Put this calculator on your own site
A working 1rm, free for any site, with no ads and no sign-up. It resizes to fit wherever you paste it and updates itself as this page improves.
Paste this anywhere. It works on any site, carries no ads, never expires, and always shows the current version.
One Rep Max Calculator by CalculateItNow
The page's own title. The clearest description of what the link leads to.
The credit line sits outside the widget on purpose, so it is a real link on your page rather than one buried in a frame. Please keep it — it is what pays for CalculateItNow staying free and ad-free. The script only resizes the widget to fit its contents; drop it and the widget still works.
Browse every calculator widget·How to add it to WordPress, Squarespace or Wix
Related calculators
The questions people ask next to a 1rm.
Calories burned for 30+ activities using 2011 Compendium of Physical Activities MET values, scaled to your weight and duration, gross and net of resting.
Daily protein in grams from body weight and goal, with cited g/kg ranges for sedentary, endurance, strength and fat-loss goals, plus a per-meal split.
Estimate lean body mass with the Boer, James and Hume formulas, or directly from a measured body fat percentage, and see what share of your weight is lean tissue.
Estimate body fat percentage with the US Navy tape method, cross-check it against the BMI formula, and see your fat mass, lean mass and ACE category.
Max heart rate by the Tanaka, 220−age or Gellish formula and five training zones in bpm — by percent of max or the Karvonen heart-rate-reserve method.
Convert pounds, ounces, stone, kilograms, grams, milligrams and tons in one go using the exact 1959 definitions — with a body-weight table and cooking equivalents.