Epley
1RM = weight × (1 + reps ÷ 30)A simple linear prediction equation commonly used for low-repetition sets.
Free strength estimator
One Rep Max (1RM) Calculator
Estimate the heaviest load you could lift for one good-form repetition from a submaximal set. Compare Epley, Brzycki and Lombardi equations, then build percentage-based training loads from your selected estimate.
3 recognized formulas Private browser calculation 1–10 rep input range
Strength calculation
Estimate your one-repetition maximum
Enter the load you lifted and the number of clean repetitions completed. For better prediction quality, this calculator intentionally limits inputs to 1–10 reps.
Percentage load chart
Training loads from 50% to 95% of estimated 1RM
These are arithmetic percentages of your selected 1RM estimate. They are useful for planning, but they do not guarantee a specific number of repetitions.
| % of 1RM | Calculated load | Gym-friendly rounded load | General use context |
|---|---|---|---|
| 95% | — | — | Very heavy practice |
| 90% | — | — | Heavy strength work |
| 85% | — | — | Strength-focused work |
| 80% | — | — | Moderately heavy work |
| 75% | — | — | General strength / volume |
| 70% | — | — | Moderate training load |
| 65% | — | — | Technique / volume |
| 60% | — | — | Technique / warm-up work |
| 55% | — | — | Light technique work |
| 50% | — | — | Warm-up / skill practice |
Rounded loads use 0.5 kg steps or 1 lb steps for convenience. Adjust to the plates, dumbbells or machine increments you actually have available.
Calculation method
How the 1RM formulas work
Each equation uses the same two inputs—load and repetitions—but applies a different mathematical model to estimate the load for one maximal repetition.
Brzycki
1RM = weight ÷ (1.0278 − 0.0278 × reps)A widely studied repetitions-to-failure equation that has performed well in lower-rep bench-press testing.
Lombardi
1RM = weight × reps0.10A nonlinear equation included to show how different modeling assumptions can shift the estimate.
Accuracy & limitations
A predicted 1RM is most useful as a repeatable benchmark
Studies comparing submaximal repetition equations show that prediction quality varies by exercise, population and repetition count. Lower-repetition sets generally predict maximum strength better than higher-repetition sets.
Keep reps low
This calculator limits estimates to 10 reps because research has found better prediction accuracy from lower-repetition tests such as 5RM compared with 10–20RM testing.
Keep technique consistent
Changing range of motion, tempo, equipment, grip or exercise variation can change the relationship between your submaximal set and actual 1RM.
Track the same equation
For progress monitoring, consistency is often more useful than chasing whichever formula gives the highest number. Use the same exercise, setup and equation over time.
Practical strength use
How to get a better estimate
Prediction equations work best when your input set reflects your real current capacity while preserving safe, repeatable technique.
Warm up progressively
Use lighter sets before your test set so the working weight does not feel artificially difficult because you are cold or unprepared.
Use one exercise variation
A barbell bench press estimate should not be treated as interchangeable with a dumbbell press, machine press or a different range of motion.
Stop if technique breaks down
Count only repetitions completed with the form standard you intend to train. Pain, unusual symptoms or loss of control are reasons to stop the set.
Retest under similar conditions
Sleep, fatigue, recent training and equipment can all change performance. Similar conditions make trend comparisons more meaningful.
Tool guide
Understand and use the One Rep Max Calculator
Use these tool-specific notes to understand the method, enter better data, interpret the output, and apply the result appropriately.
Estimated 1RM
A 1RM calculator predicts the heaviest single repetition from a submaximal set. It is useful for programming when a true maximal attempt is unnecessary or inappropriate.
Pick a Formula
Epley, Brzycki, and Lombardi use different mathematical relationships, so estimates can diverge. Comparing formulas helps show that e1RM is not an exact measured max.
Use Quality Reps
Enter a technically valid set performed close enough to your actual capacity for the equation to be meaningful. High-rep or non-standard sets generally increase prediction uncertainty.
Program From e1RM
Use estimated 1RM to choose training loads and track trends, then adjust for exercise, fatigue, equipment, technique, and the athlete’s response rather than treating percentages as exact.
Frequently asked questions
One Rep Max Calculator FAQs
Practical answers about this tool's inputs, method, results, limitations, and common real-world use.
What is a one-rep max?
Your one-repetition maximum is the greatest load you can successfully lift for one repetition of a specific exercise under a defined technique standard. This page estimates that value from a lighter multi-rep set.
Which 1RM formula is best?
No single formula is always best for every exercise and lifter. Epley and Brzycki are widely used; the comparison helps show the uncertainty rather than hiding it.
Why does this calculator stop at 10 reps?
Prediction error generally increases as repetition counts rise. Research comparing multiple-RM tests has found lower-rep testing, especially around 5RM, more accurate than 10–20RM approaches for estimating 1RM.
Should I actually attempt the predicted 1RM?
Not automatically. A predicted value is useful for programming and trend tracking. Maximal testing requires appropriate exercise skill, preparation, equipment, spotting/safety systems and judgment.
Are kilograms and pounds equally accurate?
Yes. The equation is unit-agnostic as long as the same unit is used consistently. The calculator converts the final result for convenience.
Does 80% of 1RM always equal the same number of reps?
No. Repetition capacity at a percentage of 1RM varies by exercise, training history, muscle group, fatigue and individual physiology. The table therefore shows loads, not guaranteed rep targets.
What rep range is best for estimating 1RM?
Lower-to-moderate rep sets are generally more useful than very high-rep sets because fatigue and endurance contribute less to the prediction. The exact useful range varies by exercise and lifter.
Is a 1RM estimate specific to the exercise I performed?
Yes. A bench-press e1RM should not be transferred directly to a different press variation, machine, grip, range of motion, or lifting technique.
Do I need to test a true 1RM to use the calculator?
No. The point of an e1RM is to estimate maximal strength from a submaximal set. A true 1RM test requires appropriate skill, preparation, equipment, and safety considerations.
Why can my estimated 1RM change when I am fatigued?
The input set reflects your performance that day. Sleep, prior training, warm-up, motivation, technique, and fatigue can change repetitions completed at a given load and therefore change the estimate.
Method & references
Evidence behind the estimator
The calculator uses published repetition-prediction equations and intentionally limits the input range to reduce the error associated with high-repetition estimation.
- Peer-reviewed comparison summarizing Epley, Brzycki, Lander, Mayhew, O’Connor, Wathan and other 1RM prediction equations.
- Mayhew et al.: muscular-endurance repetitions to predict bench-press strength; Brzycki performed well when 10 or fewer reps were completed.
- Reynolds et al.: 5RM testing produced greater 1RM prediction accuracy than 10RM and 20RM testing for chest press and leg press.
- Clinical rehabilitation commentary documenting the Lombardi-style equation: 1RM = rep weight × reps0.1.
- 2025 cross-validation study: repetitions-to-failure equations remain exercise- and population-dependent.
Content reviewed: .
Strength-testing disclaimer
This calculator estimates strength from a submaximal set; it does not confirm that a maximal lift is safe or achievable on a given day. Do not use pain, injury, dizziness, chest symptoms, uncontrolled medical conditions or poor technique as a reason to test harder. If maximal resistance exercise is not appropriate for you, use a qualified health or fitness professional for individualized guidance.