One Rep Max Calculator
Compare six common estimates from a near-limit set of 10 reps or fewer. The result is a starting point, not a measured maximum or a prescribed training weight.
How to Use This Calculator
Enter the weight and reps from a recent set performed close to your current rep limit with consistent technique. This tool accepts 1–10 reps. A set stopped well before your limit will tend to understate your maximum.
You'll see six formula estimates and their unweighted average for comparison. The percentage table shows example arithmetic based on that average; it does not predict how many reps you can complete or prescribe your working weights.
Understanding the Formulas
These formulas convert a completed set into different estimates. None has been shown to be the most accurate for every exercise and lifter:
Epley
Adds a linear adjustment for each rep.
Brzycki
Uses an inverse relationship between reps and load.
Lombardi
Uses a power function.
Mayhew
Uses a nonlinear exponential function.
O'Conner
Adds a smaller linear adjustment per rep.
Wathan
Uses a different nonlinear exponential function.
The average summarizes the six outputs. It has not been validated as a better predictor than each formula, so do not treat it as a guaranteed training target.
When to Test Your 1RM vs. Estimate It
A measured 1RM requires a maximal successful attempt with the intended technique. A single rep at a lighter load is not necessarily your maximum.
An estimate avoids a maximal attempt, but prediction error varies. Use your completed training sets and planned effort to decide whether a calculated load is appropriate for the next session.
Use Estimates For
- Programming training percentages
- Tracking strength progress over time
- Comparing similar sets over time
Test Your Actual 1RM If
- Preparing for a powerlifting competition
- Need a measured benchmark for a specific goal
- Have specific max strength goals
If you do test, use an appropriate warm-up, lifting setup, and a spotter or safety equipment when the lift calls for it. Avoid using a calculator result as an instruction to attempt that weight.
How to Use Your 1RM for Programming
Some programs calculate example loads as percentages of a measured or estimated 1RM. If you use an estimate, adjust the load to the planned reps, technique, and effort rather than assuming the percentage is exact.
The number of reps possible at a given percentage varies by exercise and person. The table above is arithmetic, not a universal reps-to-weight chart.
MySetPlan plans use effort targets alongside reps. The target helps you select a load that fits the session rather than relying on a fixed percentage alone.
Research behind these limits
Reynolds and colleagues (2006) found better prediction from 5-rep than 10- or 20-rep tests in their bench-press and leg-press sample.
Roberts and colleagues (2025) cross-validated published equations in bench press and leg extension; accuracy depended on the exercise and equation tested. These studies do not validate a universal accuracy percentage for this calculator.
Frequently Asked Questions
How accurate is a 1RM calculator?
There is no universal accuracy percentage. Prediction error varies by exercise, person, formula, and how close the input set was to your rep limit. Studies of common equations generally found better accuracy with fewer repetitions. Treat every output as an estimate, not a tested maximum.
Which 1RM formula is most accurate?
No formula in this tool is proven best for every lift and person. Compare the six estimates to see how much they disagree. Their unweighted average is shown for comparison; it is not a validated best estimate.
Should I actually test my one rep max?
A true 1RM is the heaviest load you can lift once with the required technique. A calculator gives an estimate without a maximal attempt, but the estimate can be wrong. If you decide to test a heavy lift, use appropriate setup, warm-up, and a spotter or safety equipment when the lift calls for it.
How often should I recalculate my 1RM?
Recalculate when a comparable near-limit set shows a meaningful performance change. Use the same exercise and technique so the estimates are easier to compare. There is no fixed interval that works for everyone.
What's a good 1RM for bench press, squat, or deadlift?
A useful target depends on your exercise, technique, training history, and goals. This calculator cannot set a personal standard from your sex or bodyweight. Compare consistent lifts over time and judge the number in the context of your own training.
Related Exercises
Get a Personalized Workout Plan
Your training history is one part of the picture. Get a plan Ely reviews against your goals, equipment, schedule, and stated limitations before delivery.
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