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One Rep Max Calculator.

Calculate your one rep max and training percentages

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01

Set your values

Results update as you type.

Several Formulas, One Estimate

Different 1RM formulas disagree slightly, especially at higher rep counts. This calculator averages several of them and shows the range they produce.

Your Estimated 1RM

115.3 lbs

Range: 112.5 - 119.0 lbs

Training Weights by Percentage

95%
Near maximal(2 reps)
109.5 lbs
90%
Heavy strength(3-4 reps)
103.8 lbs
85%
Strength(5-6 reps)
98.0 lbs
80%
Power(6-8 reps)
92.2 lbs
75%
Hypertrophy(8-10 reps)
86.5 lbs
70%
Muscular endurance(10-12 reps)
80.7 lbs
65%
Light endurance(12-15 reps)
74.9 lbs
60%
Warm-up(15+ reps)
69.2 lbs
Strength level: Beginner

Strength level

Beginner
Formula agreement: ±3.3 lbs

Formula agreement

±3.3 lbs
Confidence: High

Confidence

High

Safety Guidelines

  • These are estimates — never load a bar purely on a calculated number.
  • Accuracy is best from sets of 10 reps or fewer and drops sharply above that.
  • Warm up thoroughly with progressively heavier sets before anything near maximal.
  • Stop the set when form breaks down; use a spotter or safety bars for heavy attempts.

Training Tips

  • Retest every 8 to 12 weeks rather than chasing a new max each week.
  • Most training sits between 65% and 85% of your 1RM.
  • Strength work favours heavier weights for fewer reps; hypertrophy favours more reps.
  • Your 1RM shifts with sleep, food, and stress — treat it as a moving target.
  • Estimate from a set taken close to failure for a more useful number.

Cite this calculator

Canonical URL: https://mathify.one/en/fitness/one-rep-max

Cite as: Mathify. (2026). One Rep Max Calculator. https://mathify.one/en/fitness/one-rep-max

Use Cases

Plan your training loads

Use your estimated 1RM to set appropriate weights for different rep ranges, such as 70-80% for hypertrophy or 85-95% for strength.

Example: If your estimated 1RM is 200 lbs, you might use 140-160 lbs for sets of 8-12 reps.

Track strength progress

Monitor your estimated 1RM over time to see if your strength is improving, even if you don't test a true one rep max.

Example: Compare your estimated 1RM from last month to this month to see gains.

Frequently Asked Questions

How is my one rep max calculated?
The calculator uses the weight and reps you enter from a completed set to estimate the maximum weight you could lift for a single repetition. It applies a standard formula (like Epley or Brzycki) to provide an estimate, not an exact measurement.
Can I use this calculator for any exercise?
Yes, you can use it for any lift where you perform a set to near failure, such as bench press, squat, deadlift, or overhead press. The estimate is most accurate for compound lifts and when the set is performed with good form.
Is the one rep max estimate accurate?
The estimate is a good reference point but may vary from your actual 1RM due to factors like fatigue, technique, and muscle fiber composition. It's best used for planning training loads, not for predicting competition performance.

Tips & Common Mistakes

Tips

  • For the most accurate estimate, use a weight you can lift for 2-10 reps with good form, leaving 1-2 reps in reserve.
  • Perform your set to near failure, but avoid going to absolute failure to reduce injury risk.
  • Use the same formula consistently when tracking progress to ensure comparisons are valid.
  • Re-test your estimated 1RM every 4-6 weeks to adjust your training loads.

Common Mistakes to Avoid

  • Using a weight that is too light (e.g., 20+ reps) can overestimate your 1RM.
  • Using a weight that is too heavy (e.g., 1-2 reps) may underestimate your 1RM due to fatigue or technique breakdown.
  • Not accounting for exercise type: the estimate is less accurate for isolation movements or exercises with a steep learning curve.

Last updated: August 13, 2026