One Rep Max Calculator
Estimate your 1RM from any lift and reps using Epley and Brzycki formulas.
What it does
One rep max is the heaviest load you can lift once with good form. Testing it directly is draining and risky, so lifters estimate it from a hard submaximal set instead. Two formulas dominate: Epley, which adds a rep fraction, and Brzycki, which bends the curve for higher reps.
The tool above runs both from your weight and reps, then prints 85% of their average, a bread and butter intensity for strength sets of five.
Both formulas assume a true near max set of 2 to 10 reps. Easy sets with reps left in reserve inflate the estimate, and grinders with broken form do the same. Use honest reps or the numbers lie.
How to use
- Enter the loaded weight exactly as on the bar, in kg or lb.
- Enter clean full range reps finished close to failure.
- Read both estimates. Your true max usually sits between them.
- Base training percentages on the lower of the two when in doubt.
Formula
- reps / 30
- Epley growth per rep past one.
- 36 / (37 - reps)
- Brzycki multiplier curving upward with reps.
Epley grows linearly with reps while Brzycki curves upward, so Brzycki reads slightly lower in the mid rep range. The two agree at one rep and split by a few percent at ten, which is the honest error band of any estimate.
Worked example
Example: 100 kg for 5 reps
Squat 100 kg, 5 full reps, nothing left for a sixth.
- Epley: 100 x (1 + 5/30) = 100 x 1.1667 = 116.7 kg.
- Brzycki: 100 x 36 / (37 - 5) = 3600 / 32 = 112.5 kg.
- Average: (116.7 + 112.5) / 2 = 114.6 kg.
- 85% load: 114.6 x 0.85 = 97.4 kg for working sets.
Reference table
| Reps | Share of 1RM | Use |
|---|---|---|
| 1 | 100% | Testing, competition |
| 3 | 90 to 93% | Heavy strength |
| 5 | 85 to 87% | Strength sets |
| 8 | 78 to 81% | Hypertrophy |
| 10 to 12 | 72 to 77% | Volume work |
Limits
- Estimates within a few percent, not measured maxes.
- Breaks past 10 to 12 reps.
- Best for basic barbell lifts with standard form.
- Daily strength swings with sleep and fatigue.
Common mistakes
- Counting half reps, which inflates the estimate beyond your real strength.
- Using a fresh personal best set done on peak day as everyday math.
- Applying the formulas past 12 reps, where both drift high.
- Rounding the bar load down and the reps up in the same set.
- Testing maxes weekly instead of building with submaximal percentages.
Try it yourself
Quick checks. Answers sit tucked under each question.
80 kg for 8 reps?
Epley 80 x 1.2667 = 101.3. Brzycki 80 x 36/29 = 99.3.
Single at 100 kg?
Both formulas return 100. A single is already the max.
Questions
Epley or Brzycki: which is right?
Neither exactly. Epley suits lower reps, Brzycki mid reps. Plan from their average or the lower one.
How often should I test a true max?
Rarely. Most programs test every 8 to 12 weeks and estimate between tests.
Do the formulas work for all lifts?
Best for squat, bench, deadlift, and press with standard form. Technical Olympic lifts estimate poorly.
Why do reps past 10 break it?
Endurance and conditioning limit the set before pure strength does, so the rep count overstates the max.
What percent should beginners use?
Start near 70 to 80% of the estimate for sets of 5 to 8 and add load slowly with clean form.