One Rep Max Calculator
Estimate your one-rep max (1RM) for any lift without having to actually attempt a maximal single rep, using the widely used Epley formula.
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This is an estimate — your actual one-rep max depends on factors like fatigue, technique, and the specific lift, and can vary from this formula's prediction.
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How One-Rep Max (1RM) Estimation Works
Your one-rep max is the maximum weight you could lift for a single repetition of an exercise. Rather than testing this directly (which carries injury risk, especially untrained), it's commonly estimated from a lighter set taken close to failure.
How to Calculate One-Rep Max
This calculator uses the Epley formula: 1RM = Weight × (1 + Reps ÷ 30).
One-Rep Max Calculator Formula
- 1RM = Weight Lifted × (1 + Reps Performed ÷ 30)
How Accurate Is a 1RM Estimate?
Estimation formulas like Epley's are most accurate in the 1-10 rep range and become less reliable at higher rep counts, where fatigue and muscular endurance play a larger role than pure strength. Treat the result as a solid planning estimate, not an exact number.
One-Rep Max Examples
Moderate rep set: 185 lbs for 5 reps. 1RM = 185 × (1 + 5/30) ≈ 215.8 lbs.
Higher rep set: 135 lbs for 10 reps. 1RM = 135 × (1 + 10/30) = 180 lbs.
Common One-Rep Max Estimation Mistakes
Using a set that wasn't close to failure — the formula assumes your entered reps represent close to your maximum effort at that weight, not a comfortable submaximal set. Using rep counts above about 10-12, where estimation accuracy drops meaningfully. Testing an actual 1RM without a spotter or proper warm-up — most lifters are better served by an estimate than a maximal single-rep attempt, especially without experience.
How to Use This Calculator
Enter the weight you lifted and the number of reps you performed with good form (most accurate for sets of 10 reps or fewer).
Formula & Methodology
Epley formula: 1RM = Weight × (1 + Reps ÷ 30). This is one of the most commonly used and cited formulas for estimating one-rep max from a submaximal set.
Example: 185 lbs for 6 reps
1RM = 185 × (1 + 6/30) = 185 × 1.2 = 222 lbs estimated one-rep max.
The Epley formula (like all 1RM formulas) is most accurate for sets of about 10 reps or fewer — accuracy decreases for higher-rep sets. Individual results vary; this should be used as a training guideline, not a precise prediction.
This is a general fitness estimate, not medical or professional coaching advice. Always use proper form and appropriate spotting/safety equipment, especially when testing near-maximal lifts.
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Related Guides
- How One-Rep Max Is Calculated: Formulas, Accuracy & ExamplesCalculate your 1RM from submaximal lifts using Epley, Brzycki, and Lander formulas. Understand which formula is most accurate, and how to use 1RM percentages for training intensity.
- How Running Pace Is Calculated: Pace, Speed & Race Time ExplainedUnderstand how running pace is calculated from speed, how to convert minutes-per-mile to mph, and how to predict race finish times at any distance from 5K to marathon.
- One Rep Max Calculator: How to Estimate Your 1RM SafelyCalculate your one-rep max (1RM) for squat, bench, deadlift, and other lifts using submaximal rep formulas. Covers Epley, Brzycki, and other prediction equations with accuracy notes.
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Frequently Asked Questions
- How is one-rep max calculated here?
- Using the Epley formula: 1RM = weight lifted × (1 + reps ÷ 30) — one of the most widely used formulas for estimating a one-rep max from a submaximal set.
- How accurate is this estimate?
- It's most accurate for sets of about 10 reps or fewer. Individual results vary based on muscle fiber type, fatigue, and technique — treat it as a training guideline, not an exact prediction.
- Should I actually attempt my estimated 1RM?
- Not without proper preparation, form, and safety equipment (like a spotter or safety bars) — this calculator is meant to guide training percentages, not necessarily to be tested directly.
Last updated 7/12/2026