One Rep Max Calculator (1RM)

Enter the weight you lifted and the number of repetitions you completed, and the One Rep Max Calculator (1RM) estimates the maximum weight you could lift for a single rep. Choose your preferred unit (kg or lb), pick a formula (Epley, Brzycki, or others), and get your 1RM estimate alongside a full repetition percentage breakdown showing target weights for 1–10 reps.

Disclaimer: This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any health-related decisions.

The weight you lifted for the set

Number of reps completed with the above weight (1–30)

Epley is the most widely used formula

Results

Estimated 1RM

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90% of 1RM (2–3 reps)

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80% of 1RM (5–6 reps)

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70% of 1RM (8–10 reps)

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60% of 1RM (12–15 reps)

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Results Table

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Frequently Asked Questions

What is a one rep max (1RM)?

A one rep max (1RM) is the maximum weight you can lift for a single complete repetition of a given exercise with proper form. It represents the peak force your muscles can generate and is commonly used as a benchmark in strength training and weightlifting competitions.

How accurate is the 1RM calculator?

The calculator provides an estimate based on a mathematical formula. For best accuracy, use a weight you can lift between 1 and 10 reps — results become less reliable as rep counts increase beyond 10. The estimate is a useful training guide, but actual tested 1RM values may differ slightly.

Which formula is the best for calculating 1RM?

The Epley formula is the most widely used and generally reliable for most lifters. The Brzycki formula tends to be more conservative and is also popular. If you find one formula consistently over- or underestimates your actual max, try switching to another. Using a weight you lifted for fewer reps (3–5) improves accuracy across all formulas.

How do I calculate my one rep max without a calculator?

Using the Epley formula: 1RM = Weight × (1 + Reps / 30). For example, if you lifted 100 kg for 5 reps: 1RM = 100 × (1 + 5/30) = 100 × 1.167 ≈ 117 kg. You can also use the Brzycki formula: 1RM = Weight × (36 / (37 − Reps)).

Why is knowing my 1RM important?

Your 1RM is used to set training intensities as a percentage of your maximum. Strength programs typically prescribe loads as a percentage of 1RM (e.g. 80% for hypertrophy, 90%+ for maximal strength). It also lets you track progress objectively over time and compare performance across lifters.

Should I actually attempt a one rep max lift?

Testing your true 1RM carries injury risk, especially without a spotter or proper warm-up. Using a submaximal weight and a formula to estimate your 1RM is a safer approach, particularly for beginners. If you do test your 1RM, ensure you are well-rested, properly warmed up, and have an experienced spotter present.

Does my 1RM transfer between different exercises?

No — your 1RM is specific to each exercise. Your bench press 1RM will be very different from your squat or deadlift 1RM. Different muscles, movement patterns, and leverage points are involved in each lift, so always calculate your 1RM separately for each exercise you train.

What percentage of 1RM should I train at?

Training zones are typically: 90–100% for maximal strength (1–3 reps), 75–85% for strength and hypertrophy (5–8 reps), 65–75% for hypertrophy (8–12 reps), and 50–65% for muscular endurance (15+ reps). The right percentage depends on your training goal and program.