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One Rep Max (1RM) Calculator

Estimate your maximum single-rep lift from submaximal sets without risk of injury.

Complete Guide

Overview

Your One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. Knowing your 1RM is essential for structured strength training — programming is typically based on percentages of 1RM. This calculator provides a safe estimate without attempting a true max lift.

How to Use

Load a weight you can lift for 2–10 reps with good form.

Perform as many reps as possible (stop at technical failure).

Enter the weight and reps into the calculator.

Click Calculate for your estimated 1RM.

Formula & Calculation

Epley: 1RM = Weight × (1 + Reps/30)
Brzycki: 1RM = Weight × 36/(37 – Reps)
(Most accurate for 2–10 rep ranges)

Example

80kg × 8 reps → Epley: 80×(1+8/30) = **101 kg**, Brzycki: 80×36/29 = **99 kg**

Benefits of Using This Calculator

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Safe Testing

Estimate max without the risk of a true 1RM attempt.

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Program Design

Set accurate training percentages for your program.

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Track Strength

Monitor strength gains over time.

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Precise Loading

Know exactly what weights to use at each intensity.

Pro Tips

Best accuracy with 2–10 reps.
Higher rep counts give less accurate 1RM estimates.
Rest fully (3–5 min) between heavy sets when testing.
Use proper form — a 1RM estimate is only as good as the reps that generate it.

In-Depth Guide

One Rep Max Calculator: Estimate Your Strength Safely

Attempting a true one-rep max without a spotter is risky. But knowing your maximum lifting capacity is essential for programming strength training correctly. This calculator gives you a safe, accurate estimate from a submaximal set — no injury risk required.

What Is One Rep Max?

Your 1RM is the maximum weight you can lift for exactly one repetition with good form. It is the standard reference for strength programming — most exercises are prescribed at a percentage of 1RM. Without it, training percentages are just arbitrary numbers.

The Formulas

Epley: 1RM = Weight × (1 + Reps ÷ 30)
Brzycki: 1RM = Weight × 36 ÷ (37 − Reps)
Result = Average of both

Worked Example

85 kg for 6 reps with good form:

Epley: 85 × 1.20 = 102 kg | Brzycki: 85 × 36/31 = 98.7 kg
Average: ~100 kg estimated 1RM

Use our One Rep Max Calculator across all your lifts instantly.

Training Percentages Reference

% of 1RM	Reps	Training Goal
50–60%	12–15+	Warm-up, endurance
65–75%	8–12	Hypertrophy (size)
75–85%	4–8	Strength
85–92%	1–4	Maximal strength

Practical Tips

Test with 3–6 rep sets. The closer to true failure, the more accurate the estimate.

Rest fully between sets. 3–5 minutes ensures each set reflects your true capacity.

Re-test every 4–6 weeks. Update your 1RM at the end of each training block to keep programming relevant.

Final Thoughts

Your 1RM is the cornerstone of structured strength programming. Know it, and your training becomes precise. Without it, you are guessing at the most important variable in the gym.

Estimate your max safely with our free One Rep Max Calculator.