One Rep Max Calculator
Estimate your one-rep max from any hard set. Enter the weight and reps, and get your 1RM by the Epley and Brzycki formulas plus a full training-percentage table.
| % of 1RM | Weight | Typical reps |
|---|---|---|
| 100% | 212 lb | 1 |
| 95% | 201 lb | 2 |
| 90% | 191 lb | 4 |
| 85% | 180 lb | 6 |
| 80% | 170 lb | 8 |
| 75% | 159 lb | 10 |
| 70% | 148 lb | 12 |
| 65% | 138 lb | 15 |
| 60% | 127 lb | 15+ |
Estimates are most accurate when the set was taken close to failure at 10 reps or fewer. Formulas are population averages — your true max varies with the lift, your training history, and leverages. Test heavy singles only with a spotter and proper warm-up.
How to use this calculator
You need one recent, honest set — not a max attempt:
- Weight lifted — the load you used on the set, in pounds or kilograms
- Reps completed — how many full reps you got; a set taken close to failure at 3–6 reps gives the most accurate estimate
You get your estimated max by both formulas, their average as the headline number, and a training-percentage table that turns the estimate into working weights for every common rep range. Tracking body composition alongside strength? The BMR, TDEE, and macro calculators cover the nutrition side.
How the estimate works
There is a consistent relationship between how much you can lift once and how much you can lift for multiple reps. Strength researchers have fit that relationship into simple formulas: Epley adds about 3.3% to the weight per rep performed, while Brzycki models the drop-off as a fraction that steepens with each rep. Around 10 reps the two agree almost perfectly; at very low or very high reps they diverge by a few percent, which is why this tool shows both rather than pretending to false precision.
The formulas assume the set was near-maximal — if you stopped at 5 reps but had 3 left in the tank, the estimate will lowball your true max. They are also most dependable on compound barbell lifts (squat, bench, deadlift, press), where the rep-to-max relationship has been studied most.
Worked example — step by step
Suppose you bench pressed 185 lb for 5 reps, close to failure:
- Epley: 185 × (1 + 5 ÷ 30) = 185 × 1.1667 = 216 lb
- Brzycki: 185 × 36 ÷ (37 − 5) = 185 × 1.125 = 208 lb
- Averaged estimate: ≈ 212 lb
From that 212 lb estimate, the table prescribes your working weights: strength sets of 4 at 90% ≈ 191 lb, hypertrophy sets of 8 at 80% ≈ 170 lb, volume sets of 12 at 70% ≈ 148 lb. That is the practical payoff — one hard set calibrates every session in your program.
How to interpret your result
Treat the estimate as a planning number, not a promise. Daily readiness swings a true max by several percent — sleep, stress, and fatigue all matter. If a program calls for 85% and the bar speed says otherwise, trust the bar. Re-estimate every few weeks from a fresh hard set rather than testing singles; the trend of your estimated 1RM over months is one of the cleanest progress measures in training.
And a safety note that bears repeating: rep-max estimating is safe by design — it never requires a grinding single. If you do attempt a true max, do it fresh, with a spotter or safety pins, after working up in small jumps.
Common mistakes to avoid
- Estimating from a high-rep set. A 15-rep set measures endurance more than strength; the formulas can overshoot badly. Use 10 reps or fewer, ideally 3–6.
- Using a set that was not close to failure. Reps in reserve deflate the estimate. Count only honest, near-maximal sets.
- Carrying one lift's max to another. Each exercise has its own 1RM — program percentages per lift.
- Never updating the number. Training to stale percentages leaves progress on the table. Re-estimate at the end of each block.
- Chasing the calculator with a max attempt on a whim. The estimate's job is to make max testing unnecessary most of the year.
This tool provides population-average estimates for training purposes and is not medical or coaching advice. Lift within your ability and use appropriate safety equipment.
How we calculate this
We compute the two most-cited rep-max formulas — Epley: 1RM = w × (1 + r ÷ 30), and Brzycki: 1RM = w × 36 ÷ (37 − r) — and average them for the headline estimate. A 1-rep input returns the entered weight unchanged. The percentage table applies standard intensity fractions to the averaged estimate; the rep counts shown per percentage are population averages drawn from strength-training research and coaching practice. Formulas are least reliable above roughly 10 to 12 reps.
Sources
Frequently asked questions
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for exactly one repetition with proper form on a given exercise. It is the standard benchmark of maximal strength and the reference point most programs use to prescribe training weights — for example, '5 sets of 5 at 80% of 1RM.'
How accurate are one-rep max calculators?
Quite accurate when the input set was 10 reps or fewer and taken close to failure — typically within a few percent for compound lifts. Accuracy falls off as reps climb, because past 10 to 12 reps muscular endurance matters more than maximal strength. For the best estimate, use a hard set of 3 to 6 reps.
Which formula does this calculator use?
It shows both of the most widely used formulas and averages them for the headline number. Epley estimates 1RM as weight × (1 + reps ÷ 30); Brzycki estimates weight × 36 ÷ (37 − reps). They agree almost exactly around 10 reps and diverge slightly at low and high rep counts, which is why seeing both is useful.
Should I actually test my true 1RM instead of estimating?
For most lifters, no — an estimate carries most of the programming value with much less risk and fatigue. True max attempts are worth it for powerlifters preparing for competition. If you do test, warm up thoroughly, take small jumps, use a spotter or safety pins, and treat a technical breakdown as the end of the test.
How do I use my 1RM to pick training weights?
Programs prescribe intensity as a percentage of 1RM. As a rule of thumb: 85 to 95% for strength work in the 2 to 6 rep range, 70 to 80% for hypertrophy sets of 8 to 12, and 60 to 70% for higher-rep volume or technique work. The table above converts your estimated max into those working weights directly.
Is my 1RM the same for every exercise?
No — a 1RM is exercise-specific. Your squat, bench press, deadlift, and overhead press maxes are separate numbers, and estimates are most reliable on big compound barbell lifts. Rep-max formulas are less dependable for small isolation exercises and machines, where fatigue behaves differently.
How often should I re-test or re-estimate my 1RM?
Every 4 to 8 weeks is plenty for most programs — often at the end of a training block. Re-estimating from a heavy set of 3 to 5 reps is a low-fatigue way to track progress and keep your percentage-based weights current as you get stronger.
Do the formulas work for both pounds and kilograms?
Yes. The formulas are unit-agnostic — they scale the weight you enter, so the result comes out in whatever unit you used. The toggle just keeps the labels consistent.