What is a one-rep max (1RM)?

A one-rep max is the maximum amount of weight you can lift for a single repetition with proper form. It's used to program training loads and track strength progress.

How accurate are 1RM calculators?

1RM calculators are most accurate with 2-6 rep sets. Accuracy decreases with higher rep counts. We use three formulas (Epley, Brzycki, Lombardi) and average them for best results.

How often should I test my 1RM?

Test your true 1RM every 8-12 weeks. Use calculator estimates for daily programming. Always warm up thoroughly and have a spotter for max attempts.

How accurate are 1RM calculators?

Most 1RM formulas are accurate within 5-10% for rep ranges of 1-10. Accuracy decreases with higher rep inputs (15+ reps). Individual factors like training experience, fatigue, and exercise technique affect results. Use the calculator for programming percentages, not as a definitive max.

Should I test my actual one rep max?

Testing your true 1RM is only necessary for competitive powerlifters. For training programming, a calculated 1RM based on a 3-5 rep set is safer and sufficient. If you do test, use a spotter, warm up progressively, and only attempt after a deload week.

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One Rep Max Calculator

Estimate your 1RM and get a full percentage-based training chart

Exercise

Weight Lifted

Reps Completed

Unit

This 1RM calculator estimates your one-rep maximum for any lift using the Epley, Brzycki, and Lombardi formulas. Enter the weight you lifted and the number of reps completed, and the calculator predicts the maximum weight you could lift for a single repetition.

Frequently Asked Questions

The most common formula is Epley: 1RM = weight × (1 + reps/30). For example, if you bench press 185 lbs for 8 reps: 1RM = 185 × (1 + 8/30) = 185 × 1.267 = ~234 lbs. This is an estimate — actual 1RM testing under a spotter is the only way to confirm.

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NinjAthlete is a performance optimization platform publishing evidence-based guides on HYROX training, peptide therapy, biohacking, and longevity science. HYROX content is informed by sub-60 competition experience (59:51, HYROX Dallas). Peptide content cites peer-reviewed research with DOI/PubMed links.

Last reviewed: April 2026|Editorial Policy

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One Rep Max Calculator

Frequently Asked Questions

How do you calculate one rep max?

How accurate are 1RM calculators?

Should I test my actual one rep max?

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