1RM Calculator - One Rep Max Estimator

Your one rep max (1RM) is the maximum weight you can lift for a single repetition on any given exercise. It is the universal reference point for setting training loads, comparing strength across bodyweights, and planning competition attempts.

This free 1RM calculator uses the RPE method to estimate your max from any working set - no grinding singles required. The RPE (Rate of Perceived Exertion) scale rates how close a set was to failure: RPE 10 means absolute maximum, RPE 8 means two reps left. Combined with your weight and rep count, the calculator projects your true 1RM.

Multiple formulas included: The Epley formula (widely used in gyms), Brzycki formula (accurate for lower rep ranges), Lombardi formula, and the Tuchscherer/RTS formula specifically calibrated for powerlifting training are all calculated and displayed together so you can see the range.

When to use this calculator: After any working set at RPE 6 or higher. Sets of 1-10 reps at RPE 7-9 give the most reliable estimates. Plug in data from your squat, bench press, deadlift, overhead press, or any barbell lift.

Once you have your 1RM, use it to set backoff set weights, check your percentile ranking, or use the RPE chart to find exact training loads at any percentage.

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E1RM Calculator

Estimate your one-rep max using the Tuchscherer RPE method

Your Set

Enter the weight you lifted for your set

How many reps you completed

6 7 8 9 10
RPE

Enter a weight to see your E1RM

Fill in the weight, reps, and RPE above and your estimated one-rep max will appear here instantly.

Estimated One Rep Max

Working Weight

% of 1RM

%

Reps @ RPE

×

Rep Max Table

Estimated weights at different rep ranges based on your E1RM

Reps RPE 10 RPE 9 RPE 8 RPE 7

Your E1RM estimated by five different formulas. The Tuchscherer RPE method is the primary calculation above.

Formula E1RM Deviation

Average E1RM

Range

-

Confidence

%

Related Calculators

RPE Chart Full percentage reference table Plate Calculator Load the right plates on the bar Backoff Sets Calculate your back-off weights

What is E1RM?

Your Estimated One Rep Max (E1RM) is the maximum weight you could theoretically lift for a single repetition. Unlike a true 1RM test, the E1RM is calculated from a submaximal set using the RPE (Rate of Perceived Exertion) scale.

This calculator uses the Tuchscherer RPE algorithm, which maps reps and RPE to a percentage of your 1RM. For example, 5 reps at RPE 8 corresponds to approximately 81.1% of your max. The formula then works backwards to estimate your true 1RM.

For the most accurate results, use sets of 1-5 reps at RPE 7-9. Higher rep ranges (6-10) are supported but tend to be less precise. Maximum effort sets (RPE 10) also introduce more estimation error.

Frequently Asked Questions

The Tuchscherer RPE-based E1RM formula is generally accurate within 2-5% for trained lifters using sets of 1-8 reps at RPE 7-9. Accuracy decreases with higher rep ranges and at extreme RPE values. The formula works best when you have experience accurately rating your RPE.
RPE 8 is the most commonly used value for E1RM estimation because it provides a clear signal (2 reps left in the tank) while keeping you away from failure. If you are unsure, err on the side of a lower RPE. Most lifters overestimate their RPE by about 0.5-1 point until they develop calibration through experience.
Daily E1RM fluctuations of 3-7% are completely normal. Factors like sleep quality, nutrition, stress, time of day, and accumulated training fatigue all affect your daily performance. Rather than fixating on a single E1RM value, track the trend over weeks to gauge true strength progress.
For most training purposes, E1RM is preferable to true 1RM testing. True 1RM attempts carry higher injury risk, require significant recovery time, and need peaking protocols to be accurate. E1RM allows you to estimate your max from regular training sets without the fatigue and risk of maximal attempts.
Most 1RM calculators use formulas like Epley or Brzycki that only account for weight and reps. The RPE-based method adds a third variable: how hard the set felt. This means a set of 5 reps at RPE 8 (2 reps left) gives a different E1RM than 5 reps at RPE 10 (failure), making the estimate significantly more accurate.

E1RM estimates are based on the Tuchscherer RPE chart and may vary from your actual one-rep max. Always use a spotter and proper safety equipment when lifting heavy weights.