One Rep Max Calculator (1RM)
Estimate your one-rep max safely and turn it into practical training weights.
Calculator inputs
Enter weight, reps, and units to calculate your 1RM.
How strong is your estimated 1RM?
Use this result to estimate 1RM for max strength estimation without pushing to a true max every session.
Estimated 1RM
Based on: 80 kg × 8 reps
Confidence is Medium because reps=8. For best accuracy, use a set of 3-8 reps.
Training Weights Based on Your 1RM
Use your estimated 1RM to map percentage-based training weights for strength training blocks.
Heavier ranges target max strength training, while moderate ranges support hypertrophy training.
Plate rounding
Toggle plate rounding to match available plates.
Training percentages
Percentages map your 1RM to target rep ranges and training goals.
Warm-up sets
Training weights
| %1RM | Weight | Typical reps | Goal |
|---|---|---|---|
| 95% | 97.5 kg | 1-2 | Max strength |
| 90% | 90.0 kg | 2-4 | Strength |
| 85% | 85.0 kg | 4-6 | Strength/volume |
| 80% | 80.0 kg | 6-8 | Hypertrophy |
| 75% | 75.0 kg | 8-10 | Hypertrophy |
| 70% | 70.0 kg | 10-12 | Hypertrophy/technique |
| 60% | 60.0 kg | 12-20 | Endurance/skill |
Advanced 1RM Options
Expand the sections below to refine your estimate with additional inputs.
Show advanced options
RPE-based 1RM estimation
RPE training helps adjust your estimated 1RM based on proximity to failure, so the number matches how the set actually felt.
Formula comparison
Compare common formulas to see how different estimates track across rep ranges.
Warm-up sets
Add warm-up sets to keep your ramp-up consistent before heavy work sets.
What Is One Rep Max (1RM)?
A one rep max is the heaviest weight you can lift once with solid form in strength training or weightlifting.
Most lifters estimate 1RM with submaximal sets because testing a true max too often adds fatigue and risk. A calculator makes the process safer while keeping your plan repeatable.
How Accurate Is This 1RM Calculator?
Estimates are most accurate in the 1-5 rep range. As reps climb, the margin of error grows because fatigue skews performance.
Use the calculator as a training guide, and prioritize safe technique, stable setups, and progressive loading.
Frequently Asked Questions
How accurate is a one rep max calculator?
Accuracy is highest at low reps because you are closer to a true max. When you estimate 1RM from 1 to 5 reps, the formulas stay conservative and repeatable.
Higher rep sets introduce more fatigue and variation, so the estimate can drift. Use it as a guide for max strength estimation and trend tracking rather than a single definitive number.
Can beginners use a 1RM calculator for strength training?
Yes. Beginners can use an estimated 1RM to guide progress without testing a true max, which keeps strength training safer while technique is still developing.
Start light, focus on form, and use the estimate to set training weights that feel controlled. Revisit the estimate as your reps and load improve.
Is 1RM useful for hypertrophy training?
Yes. A 1RM gives you a clear reference for hypertrophy training loads, even if your goal is not a maximal lift.
Most hypertrophy work sits in moderate percentages that let you accumulate volume. The estimate helps you pick weights that are challenging without sacrificing form.
How does RPE training affect 1RM estimation?
RPE training adjusts your estimated 1RM based on how close you were to failure. A hard set at a given weight usually indicates a higher estimate than an easy set with the same reps.
Tracking RPE over time helps keep the estimate honest when fatigue, stress, or technique shifts are in play.
How often should I test or estimate my 1RM?
Most lifters estimate 1RM from regular training sets every few weeks. This keeps progress visible without needing frequent max tests.
Testing a true max is best reserved for peaking phases or when you are well-rested. Use estimates the rest of the year to stay consistent.