What Is a One Rep Max (1RM)?
This one rep max calculator estimates your 1RM — the heaviest weight you can lift for a single repetition with proper form — from a set you can already do for several reps. Athletes, coaches, and lifters use 1RM to gauge strength, build training programs, and track progress.
Testing a true 1RM is risky and needs a spotter, so most lifters estimate it instead. Enter the weight you lifted and the reps you completed, and the calculator returns your 1RM as the average of 7 proven strength formulas.
Why 1RM Matters
- Programming training loads — strength programs prescribe weights as a percentage of your 1RM (for example, 5 sets of 3 at 85%).
- Tracking strength gains — compare your estimated 1RM across weeks and months to see real progress.
- Comparing lifts — understand the relative strength of your bench press, squat, and deadlift.
How to Use the 1RM Calculator
Select your exercise
Pick Bench Press, Squat, Deadlift, OHP, or Other. The choice labels your result and each history entry so you can track lifts separately.
Enter the weight
Type the weight you lifted into the Weight field. Tap the unit button to toggle between kg and lbs — the value converts automatically.
Enter the reps
Type how many repetitions you completed, or tap a Quick reps preset (1, 3, 5, 8, 10, or 12). A weight you can lift for 2 to 10 reps gives the most reliable estimate.
Read your estimated 1RM
Your Estimated 1RM updates instantly as the average of all 7 formulas. Expand the breakdown and load table below to plan your working sets.
Features
7 Proven Formulas Averaged
Estimates your 1RM with Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan, then averages the results to reduce single-formula bias.
Exercise Presets
Switch between Bench Press, Squat, Deadlift, OHP, and Other to label your result and keep each lift in its own history.
kg / lbs Conversion
Toggle units with one tap. The weight you entered converts automatically and every result updates instantly.
Quick Reps Presets
Tap a 1, 3, 5, 8, 10, or 12 rep preset to fill the reps field instantly, or type any number yourself.
Training Load Table
See the weight for every percentage from 100% down to 50% of your 1RM, with the estimated reps you can perform at each load.
Formula Breakdown
Expand the breakdown to compare each formula's individual estimate, with the highest result highlighted.
Calculation History
Recent calculations are saved automatically (up to 20). Review past results, delete single entries, or clear the whole history.
Saved Locally
Your history, unit, and exercise choice live in your browser's local storage — nothing is sent to any server.
Frequently Asked Questions
How do I calculate my one rep max without lifting it?
Enter a weight you can lift for several reps and the number of reps you completed. The calculator applies 7 submaximal formulas and averages them to estimate the single-rep maximum, so you never have to attempt the true max.
How accurate is a 1RM estimate?
For sets of 2 to 10 reps, most formulas land within roughly 5 to 10% of your true 1RM. Accuracy drops as reps climb, especially above 10. Averaging 7 formulas helps balance out the bias of any single equation.
Why do the formulas give different results?
Each formula was derived from a different study with different populations and training levels. Some, like Epley, estimate higher at high rep counts, while others, like Brzycki, stay more conservative. The average gives a balanced figure, and you can expand the Formula Breakdown to compare them.
What rep range gives the most accurate result?
A set of 3 to 5 reps generally gives the most accurate estimate. Sets of 1 to 2 reps are already close to your max and need little estimation, while sets above 10 reps add more variability to the prediction.
Should I test my actual 1RM instead?
A true 1RM attempt carries more injury risk than submaximal testing. If you do try it, use a spotter, warm up thoroughly, and only attempt it well-rested. For most training purposes, an estimated 1RM works just as well.
Does the exercise I pick change the calculation?
No. The formulas are identical for every exercise. The exercise selector only labels your result and history entries, making it easy to track bench, squat, and deadlift separately.
Is my data stored privately?
Yes. Your history, unit, and exercise preferences are stored only in your browser's local storage and never sent to any server. Clearing your browser data removes the saved history.
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