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One Rep Max Calculator — Find Your True Strength

One Rep Max Calculator — Find Your 1RM Strength | Free Online Tool
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One Rep Max Calculator

Calculate Your Maximum Strength · Free Instant Results

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📖 About This Calculator

Every serious lifter eventually asks the same question — how much can I actually lift for one rep?

Whether you want to program your training properly, track your strength progress over time, or just settle the debate at the gym, your One Rep Max is the number that matters. This calculator works it out from any weight and rep combination you've already done — no need to attempt a dangerous single.

Enter your weight lifted, reps completed, and exercise type. You'll get your estimated 1RM from four different scientific formulas, an averaged result, and a complete training percentage breakdown showing exactly what weights to use for every rep range in your program.

🚀 How to Use

1 Select your unit system — Metric (kg) or Imperial (lbs).
2 Enter the Weight you lifted.
3 Enter the number of Reps you completed.
4 Select your Exercise type.
5 Select your Gender.
6 Click Calculate 1RM.
7 Your One Rep Max, all four formula results, and training percentage table appear instantly.
8 Best results: Use a weight where you completed between 2 and 10 reps to failure or near-failure. The closer to failure, the more accurate the estimate.
9 Tip: Click Reset to start a new calculation.

❓ Frequently Asked Questions

Your One Rep Max — or 1RM — is the maximum weight you can lift for exactly one complete repetition with proper form. It's the universal measure of absolute strength for any given exercise. It matters because almost all serious strength programming is built around percentages of your 1RM. Knowing your 1RM lets you train with precision — instead of guessing weights, you know exactly what to load on the bar for any rep range and training goal.
Testing your true 1RM carries real injury risk, especially on compound movements like squats and deadlifts. A missed attempt at maximum weight — particularly without a spotter — can cause serious injury. That's exactly why estimated 1RM calculators exist. By lifting a submaximal weight for multiple reps, you get an accurate estimate without the risk. Most coaches recommend testing true 1RM only for experienced lifters in competition settings, or with experienced spotters in a controlled environment.
It depends on the rep range. The Epley and Brzycki formulas are the most widely used and perform well for sets of 2–10 reps. Brzycki tends to be slightly more accurate at lower rep ranges (1–5), while Epley is more reliable at higher rep ranges (6–10). The Lander formula sits between the two. This calculator averages all four to give you the most balanced estimate regardless of your rep range.
Once you know your 1RM, you can structure your entire training around it. Heavy strength work (1–5 reps) is typically done at 85–95% of 1RM. Hypertrophy training (6–12 reps) sits at 65–85%. Muscular endurance work (12+ reps) uses 50–65%. The training percentage table in this calculator gives you the exact weights for every rep range — just look up the range you're training in and load accordingly.
Strength progresses over weeks and months, so your 1RM estimate becomes outdated over time. A good rule of thumb is to retest every 6–8 weeks — either by attempting a true max (if experienced) or by running a heavy set to near-failure and recalculating. Tracking your 1RM progress over time is one of the most motivating ways to see how far your strength has come.

⚠️ Disclaimer

This One Rep Max Calculator provides estimated results based on mathematical formulas and is intended for general fitness reference only. Estimated 1RM values are not a substitute for supervised strength testing and should not be used to determine weights for competitive lifting without proper coaching and supervision.

Attempting maximum effort lifts carries inherent risk of injury. Always use proper form, appropriate warm-up, and qualified spotters when performing heavy compound lifts. If you are new to strength training or have any existing injuries or medical conditions, consult a qualified fitness professional or healthcare provider before following any strength training program.