1RM Calculator – Accurately Estimate Your One-Rep Max

1RM Calculator

Knowing your One-Rep Max (1RM) is essential for anyone serious about strength training or powerlifting. Whether you're preparing for a competition, designing a training program, or just trying to gauge your strength progress, the 1RM serves as a crucial benchmark. Our 1RM Calculator provides an easy and reliable way to estimate your 1RM using multiple well-established formulas — all from the comfort of your browser, no barbell max testing required.

This calculator is built using an intuitive interface with a clean, dark theme and bright orange highlights to enhance focus and accessibility. With just two inputs — the weight lifted and the number of repetitions performed — you get four separate 1RM estimates instantly.

✅ What Is One-Rep Max (1RM)?

The One-Rep Max is the maximum amount of weight you can lift for a single, complete repetition of a given exercise. It’s commonly used in powerlifting for the squat, bench press, and deadlift, but can also apply to other strength-based lifts like overhead press or barbell row.

Measuring your true 1RM directly can be risky, especially for beginners or during off-season training. That's where this calculator shines — it helps you determine a safe, approximate 1RM based on submaximal effort.

🧠 How the 1RM Calculator Works

Our tool uses four of the most popular 1RM prediction formulas in strength training science:

1. Epley Formula

1RM=Weight×(1+Reps30)\text{1RM} = \text{Weight} \times (1 + \frac{\text{Reps}}{30})1RM=Weight×(1+30Reps)

This is one of the most widely accepted formulas, ideal for rep ranges between 1 and 10. It assumes a linear drop in performance as reps increase.

2. Brzycki Formula

1RM=Weight×(3637−Reps)\text{1RM} = \text{Weight} \times \left( \frac{36}{37 - \text{Reps}} \right)1RM=Weight×(37−Reps36)

This method is popular in athletic training environments. It's known to be slightly conservative and best used with reps under 10.

3. McGlothin Formula

1RM=100×Weight101.3−2.67123×Reps\text{1RM} = \frac{100 \times \text{Weight}}{101.3 - 2.67123 \times \text{Reps}}1RM=101.3−2.67123×Reps100×Weight

This formula was developed using empirical data and is good for more accurate estimates in the 1–10 rep range.

4. Lombardi Formula

1RM=Weight×(Reps)0.10\text{1RM} = \text{Weight} \times (\text{Reps})^{0.10}1RM=Weight×(Reps)0.10

Lombardi’s method assumes non-linear strength curves and tends to overestimate for high reps. It’s useful for advanced lifters pushing endurance sets.

🔧 Features of the Tool

🎯 Accurate 1RM Predictions from 4 leading formulas.
🧮 Quick Input: Just enter the weight lifted and the reps completed.
💡 Responsive UI: Clean, mobile-friendly layout with orange accents.
📊 Side-by-Side Results: See all estimates in a modal popup to compare instantly.
✅ Safe and Easy: No need to risk injury by testing your real max in the gym.

💪 Why Use a 1RM Calculator?

1RM is the foundation of nearly all strength programs. Programs like 5/3/1, Juggernaut Method, Texas Method, and Linear Periodization base training percentages off your 1RM. With this calculator, you can:

Plan your weekly training loads precisely (e.g., working at 70–85% of 1RM)
Track progress without constantly maxing out
Avoid overtraining or injury from frequent max attempts
Compare your performance over time
Calculate relative strength for competitions

📈 Example Use Case

Let’s say you bench pressed 80 kg for 8 reps. Plug it into the calculator and get:

Epley: 101.3 kg
Brzycki: 100.3 kg
McGlothin: 100.6 kg
Lombardi: 95.2 kg

Now you know your bench 1RM is ~100 kg, and you can confidently train with percentages like 70 kg (70%), 80 kg (80%), and 90 kg (90%) for volume and intensity sessions.

📌 Best Practices

For accuracy, only use reps between 1 and 10.
Use consistent tempo — no cheating, bouncing, or assisted reps.
Always round down slightly if training unsupervised.
Recalculate every 4–6 weeks as you get stronger.

🚀 Ready to Find Your 1RM?

Our 1RM calculator is fast, lightweight, and doesn’t require login or account creation. Simply enter your lift numbers, hit “Calculate,” and get instant feedback. Whether you’re a beginner or a competitive powerlifter, this tool helps you stay strong, safe, and smart.

Estimated 1RM